AArch32: Add ARM platform changes in BL2

This patch adds ARM platform changes in BL2 for AArch32 state.
It instantiates a descriptor array for ARM platforms describing
image and entrypoint information for `SCP_BL2`, `BL32` and `BL33`.
It also enables building of BL2 for ARCH=aarch32.

Change-Id: I60dc7a284311eceba401fc789311c50ac746c51e
diff --git a/Makefile b/Makefile
index aaf84db..2b630b3 100644
--- a/Makefile
+++ b/Makefile
@@ -522,13 +522,13 @@
 include bl1/bl1.mk
 endif
 
-# For AArch32, BL31 is not applicable, and BL2 & BL2U are not supported at present.
-ifneq (${ARCH},aarch32)
 ifdef BL2_SOURCES
 NEED_BL2 := yes
 include bl2/bl2.mk
 endif
 
+# For AArch32, BL31 is not applicable, and BL2U is not supported at present.
+ifneq (${ARCH},aarch32)
 ifdef BL2U_SOURCES
 NEED_BL2U := yes
 include bl2u/bl2u.mk