AArch32: Common changes needed for BL1/BL2

This patch adds common changes to support AArch32 state in
BL1 and BL2. Following are the changes:

* Added functions for disabling MMU from Secure state.
* Added AArch32 specific SMC function.
* Added semihosting support.
* Added reporting of unhandled exceptions.
* Added uniprocessor stack support.
* Added `el3_entrypoint_common` macro that can be
  shared by BL1 and BL32 (SP_MIN) BL stages. The
  `el3_entrypoint_common` is similar to the AArch64
  counterpart with the main difference in the assembly
  instructions and the registers that are relevant to
  AArch32 execution state.
* Enabled `LOAD_IMAGE_V2` flag in Makefile for
  `ARCH=aarch32` and added check to make sure that
  platform has not overridden to disable it.

Change-Id: I33c6d8dfefb2e5d142fdfd06a0f4a7332962e1a3
diff --git a/plat/arm/board/common/board_common.mk b/plat/arm/board/common/board_common.mk
index 49136e6..a6d4ce7 100644
--- a/plat/arm/board/common/board_common.mk
+++ b/plat/arm/board/common/board_common.mk
@@ -31,10 +31,8 @@
 PLAT_INCLUDES		+=	-Iinclude/plat/arm/board/common/			\
 				-Iinclude/plat/arm/board/common/drivers
 
-PLAT_BL_COMMON_SOURCES	+=	drivers/arm/pl011/${ARCH}/pl011_console.S
-ifeq (${ARCH}, aarch64)
-PLAT_BL_COMMON_SOURCES	+=	plat/arm/board/common/aarch64/board_arm_helpers.S
-endif
+PLAT_BL_COMMON_SOURCES	+=	drivers/arm/pl011/${ARCH}/pl011_console.S		\
+				plat/arm/board/common/${ARCH}/board_arm_helpers.S
 
 BL1_SOURCES		+=	plat/arm/board/common/drivers/norflash/norflash.c