feat(bl): add interface to query TF-A semantic ver

Adding interface for stand-alone semantic version of TF-A
for exporting to RSS attestation, and potentially other areas
as well.

Signed-off-by: Lauren Wehrmeister <lauren.wehrmeister@arm.com>
Change-Id: Ib4a2c47aa1e42a3b850185e674c90708a05cda53
diff --git a/Makefile b/Makefile
index ee5e2e7..dd46f95 100644
--- a/Makefile
+++ b/Makefile
@@ -9,6 +9,7 @@
 #
 VERSION_MAJOR			:= 2
 VERSION_MINOR			:= 7
+VERSION				:= ${VERSION_MAJOR}.${VERSION_MINOR}
 
 # Default goal is build all images
 .DEFAULT_GOAL			:= all
@@ -322,7 +323,7 @@
 ifeq (${BUILD_STRING},)
         BUILD_STRING  :=  $(shell git describe --always --dirty --tags 2> /dev/null)
 endif
-VERSION_STRING    :=  v${VERSION_MAJOR}.${VERSION_MINOR}(${BUILD_TYPE}):${BUILD_STRING}
+VERSION_STRING    :=  v${VERSION}(${BUILD_TYPE}):${BUILD_STRING}
 
 ifeq (${AARCH32_INSTRUCTION_SET},A32)
 TF_CFLAGS_aarch32	+=	-marm