qemu: Implement qemu_system_off via semihosting. ...

This makes the PSCI SYSTEM_OFF call work on QEMU. It assumes that QEMU has
semihosting enabled, but that is already assumed by the image loader.

Signed-off-by: Andrew Walbran <qwandor@google.com>
Change-Id: I0fb7cf7909262b675c3143efeac07f4d60730b03

Standardise header guards across codebase ...

All identifiers, regardless of use, that start with two underscores are
reserved. This means they can't be used in header guards.

The style that this project is now to use the full name of the file in
capital letters followed by 'H'. For example, for a file called
"uart_example.h", the header guard is UART_EXAMPLE_H.

The exceptions are files that are imported from other projects:

- CryptoCell driver
- dt-bindings folders
- zlib headers

Change-Id: I50561bf6c88b491ec440d0c8385c74650f3c106e
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

Use SPDX license identifiers ...

To make software license auditing simpler, use SPDX[0] license
identifiers instead of duplicating the license text in every file.

NOTE: Files that have been imported by FreeBSD have not been modified.

[0]: https://spdx.org/

Change-Id: I80a00e1f641b8cc075ca5a95b10607ed9ed8761a
Signed-off-by: dp-arm <dimitris.papastamos@arm.com>

Remove variables from .data section ...

Update code base to remove variables from the .data section,
mainly by using const static data where possible and adding
the const specifier as required. Most changes are to the IO
subsystem, including the framework APIs. The FVP power
management code is also affected.

Delay initialization of the global static variable,
next_image_type in bl31_main.c, until it is realy needed.
Doing this moves the variable from the .data to the .bss
section.

Also review the IO interface for inconsistencies, using
uintptr_t where possible instead of void *. Remove the
io_handle and io_dev_handle typedefs, which were
unnecessary, replacing instances with uintptr_t.

Fixes ARM-software/tf-issues#107.

Change-Id: I085a62197c82410b566e4698e5590063563ed304

Reduce deep nesting of header files ...

Reduce the number of header files included from other header
files as much as possible without splitting the files. Use forward
declarations where possible. This allows removal of some unnecessary
"#ifndef __ASSEMBLY__" statements.

Also, review the .c and .S files for which header files really need
including and reorder the #include statements alphabetically.

Fixes ARM-software/tf-issues#31

Change-Id: Iec92fb976334c77453e010b60bcf56f3be72bd3e

Move include and source files to logical locations ...

Move almost all system include files to a logical sub-directory
under ./include. The only remaining system include directories
not under ./include are specific to the platform. Move the
corresponding source files to match the include directory
structure.

Also remove pm.h as it is no longer used.

Change-Id: Ie5ea6368ec5fad459f3e8a802ad129135527f0b3