The values of CP15BEN, nTWI & nTWE bits in SCTLR_EL1 are architecturally
unknown if EL3 is AARCH64 whereas they reset to 1 if EL3 is AArch32. This
might be a compatibility break for legacy AArch32 normal world software if
these bits are not set to 1 when EL3 is AArch64. This patch enables the
CP15BEN, nTWI and nTWE bits in the SCTLR_EL1 if the lower non-secure EL is
AArch32. This unifies the SCTLR settings for lower non-secure EL in AArch32
mode for both AArch64 and AArch32 builds of Trusted Firmware.

Fixes ARM-software/tf-issues#428

Change-Id: I3152d1580e4869c0ea745c5bd9da765f9c254947
Signed-off-by: Soby Mathew <soby.mathew@arm.com>

This patch moves the PSCI services and BL31 frameworks like context
management and per-cpu data into new library components `PSCI` and
`el3_runtime` respectively. This enables PSCI to be built independently from
BL31. A new `psci_lib.mk` makefile is introduced which adds the relevant
PSCI library sources and gets included by `bl31.mk`. Other changes which
are done as part of this patch are:

* The runtime services framework is now moved to the `common/` folder to
  enable reuse.
* The `asm_macros.S` and `assert_macros.S` helpers are moved to architecture
  specific folder.
* The `plat_psci_common.c` is moved from the `plat/common/aarch64/` folder
  to `plat/common` folder. The original file location now has a stub which
  just includes the file from new location to maintain platform compatibility.

Most of the changes wouldn't affect platform builds as they just involve
changes to the generic bl1.mk and bl31.mk makefiles.

NOTE: THE `plat_psci_common.c` FILE HAS MOVED LOCATION AND THE STUB FILE AT
THE ORIGINAL LOCATION IS NOW DEPRECATED. PLATFORMS SHOULD MODIFY THEIR
MAKEFILES TO INCLUDE THE FILE FROM THE NEW LOCATION.

Change-Id: I6bd87d5b59424995c6a65ef8076d4fda91ad5e86