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/include/common/aarch32/asm_macros.S b/include/common/aarch32/asm_macros.S
index 11e45bb..5f04499 100644
--- a/include/common/aarch32/asm_macros.S
+++ b/include/common/aarch32/asm_macros.S
@@ -70,6 +70,16 @@
 	.endm
 
 	/*
+	 * Declare the exception vector table, enforcing it is aligned on a
+	 * 32 byte boundary.
+	 */
+	.macro vector_base  label
+	.section .vectors, "ax"
+	.align 5
+	\label:
+	.endm
+
+	/*
 	 * This macro calculates the base address of the current CPU's multi
 	 * processor(MP) stack using the plat_my_core_pos() index, the name of
 	 * the stack storage and the size of each stack.