AArch32: Add BL2U support

Add support for firmware upgrade on AArch32.
This patch has been tested on the FVP models.

NOTE: Firmware upgrade on Juno AArch32 is not currently supported.

Change-Id: I1ca8078214eaf86b46463edd14740120af930aec
Signed-off-by: dp-arm <dimitris.papastamos@arm.com>
Co-Authored-By: Yatharth Kochar <yatharth.kochar@arm.com>
diff --git a/Makefile b/Makefile
index 78860b3..ddf8756 100644
--- a/Makefile
+++ b/Makefile
@@ -396,13 +396,13 @@
 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
 endif
 
+# For AArch32, BL31 is not currently supported.
+ifneq (${ARCH},aarch32)
 ifdef BL31_SOURCES
 # When booting an EL3 payload, there is no need to compile the BL31 image nor
 # put it in the FIP.