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/plat/common/platform.h b/include/plat/common/platform.h
index 852ccbc..5b4d11d 100644
--- a/include/plat/common/platform.h
+++ b/include/plat/common/platform.h
@@ -86,7 +86,7 @@
  * Optional common functions (may be overridden)
  ******************************************************************************/
 uintptr_t plat_get_my_stack(void);
-void plat_report_exception(unsigned long);
+void plat_report_exception(unsigned int exception_type);
 int plat_crash_console_init(void);
 int plat_crash_console_putc(int c);
 void plat_error_handler(int err) __dead2;