MicroLib is the lightweight C lib for the Arm toolchain and
used as the default C lib on bare metal builds with the Arm
toolchain. It requires two separate memory regions for stack
and heap.

The change is based on nRF52840.sct.

Workaround a bug where the boot stack size configuration option is not
passed on to armlink, the Arm Compiler's linker. Prefer
MBED_CONF_TARGET_BOOT_STACK_SIZE if present, as this is what the
configuration system should provide. Fall back to MBED_BOOT_STACK_SIZE
if MBED_CONF_TARGET_BOOT_STACK_SIZE is not defined, as in the case of
buggy tools. If both MBED_CONF_TARGET_BOOT_STACK_SIZE and
MBED_BOOT_STACK_SIZE are not defined, then we fall back to a hard-coded
value provided by the linkerscript. See
https://github.com/ARMmbed/mbed-os/issues/13474 for more information.

The same default value is provided in the GCC_ARM linker file.

To allow overriding of the boot stack size from the Mbed configuration
system, consistently use MBED_CONF_TARGET_BOOT_STACK_SIZE rather than
MBED_BOOT_STACK_SIZE.

Fixes #10319

ARM Compiler 6.13 testing revealed linker errors pointing out
conflicting use of `__user_setup_stackheap` and
`__user_initial_stackheap` in some targets. Remove the unwanted
`__user_initial_stackheap` from the targets - the setup is
centralised in the common platform code.

Looking into this, a number of other issues were highlighted

* Almost all targets had `__initial_sp` hardcoded in assembler,
  rather than getting it from the scatter file. This was behind
  issue #11313. Fix this generally.
* A few targets' `__initial_sp` values did not match the scatter
  file layout, in some cases meaning they were overlapping heap
  space. They now all use the area reserved in the scatter file.
  If any problems are seen, then there is an error in the
  scatter file.
* A number of targets were reserving unneeded space for heap and
  stack in their startup assembler, on top of the space reserved in
  the scatter file, so wasting a few K. A couple were using that
  space for the stack, rather than the space in the scatter file.

To clarify expected behaviour:

* Each scatter file contains empty regions `ARM_LIB_HEAP` and
  `ARM_LIB_STACK` to reserve space. `ARM_LIB_STACK` is sized
  by the macro `MBED_BOOT_STACK_SIZE`, which is set by the tools.
  `ARM_LIB_HEAP` is generally the space left over after static
  RAM and stack.
* The address of the end of `ARM_LIB_STACK` is written into the
  vector table and on reset the CPU sets MSP to that address.
* The common platform code in Mbed OS provides `__user_setup_stackheap`
  for the ARM library. The ARM library calls this during startup, and
  it calls `__mbed_user_setup_stackheap`.
* The default weak definition of `__mbed_user_setup_stackheap` does not
  modify SP, so we remain on the boot stack, and the heap is set to
  the region described by `ARM_LIB_HEAP`. If `ARM_LIB_HEAP` doesn't
  exist, then the heap is the space from the end of the used data in
  `RW_IRAM1` to the start of `ARM_LIB_STACK`.
* Targets can override `__mbed_user_setup_stackheap` if they want.
  Currently only Renesas (ARMv7-A class) devices do.
* If microlib is in use, then it doesn't call `__user_setup_stackheap`.
  Instead it just finds and uses `ARM_LIB_STACK` and `ARM_LIB_HEAP`
  itself.

* Update all scatterfiles to define MBED_RAM_START and MBED_RAM_SIZE.  These
get defined in mbed_lib.json when building with a SoftDevice but were missing
when no SoftDevice is brought in.
* Remove SDK 14.2 SoftDevice files.
* Add missing header file to qspi_api.c.

- Adjust memory for SoftDevice
    - Enable PRIO=5 for interrupt priority check
    - Change NRF_SD_BLE_API_VERSION to 6
    - Add handle and buffer for advertising and scanning
    - Remove guard for phy update
    - Change scatter files and mbed_lib.json for PR #8607

When the SoftDevice (SD) is enabled we need to set the app_offset
to 0x26000 to make room for the SoftDevice.  If we let the build
tools self-manage this, MBED_APP_START is coming out at 0x25000
which is not correct for the Nordic 15.0 SDK.

The app_offset value is translated to MBED_APP_START by the build
infrastructure.  We were hard coding MBED_APP_START in the scatter
and ld files as a temporary measure while testing.  This now sets
it properly if the SD is being brought in.

- Use new NRFX header file
- Fix nRF52832 linker script/ld files (hardcoded addresses for now)
- Temporarily remove DEVICE_TRNG for nRF52832 (which broke the build)
- Improve serial_putc() fix so we don't rely on "extra" functions

The DEVICE_FOO macros are always defined (either 0 or 1).

This patch replaces any instances of a define check on a DEVICE_FOO
macro with value test instead.

Signed-off-by: Alastair D'Silva <alastair@d-silva.org>

--legacyalign, --no_legacyalign are deprecated from ARMC6 compiler, in order to
remove deprecated flags all linker files (GCC and IAR as well to have uniformity)
should strictly align to 8-byte boundary

Feature itm fix

IAR linker script was using memory settings from the NRF52840 and
not the NRF52832.

The ITM must be initialized before the SoftDevice, but due to the
lazy initialization in C++ on (at least) GCC the ITM init call
might happen too late.

This commit moves the initialization code into the NRF52 system
startup file.

Add missing noinit section.

NRF52: add a separate .nvictable section and allow .noinit to be used…

The nrf section features has different implementations for each compilers supported by mbed-os. The header guard was ruling out compiler other than GCC by checking if __GNUC__ is defined. This check is not applicable on mbed os as the ARM compiler compile sources with gnu compatibility.

This patch makes sure that the right implementation is selected for the right compiler . The previous patch has been reverted as it is not reliable.

GCC and IAR ISR stack sizes have been set to 0x800.
(ARM compiler does not set stack size explicitly).