docs(changelog): changelog for v2.12 release

Generated this change-log using below command:
npm run release -- --skip.commit --skip.tag --release-as 2.12.0

Change-Id: Idb74f6a31bf2691e7666e2738030d6f0e2b8c519
Signed-off-by: Govindraj Raja <govindraj.raja@arm.com>
diff --git a/Makefile b/Makefile
index b0363cb..e4a1f31 100644
--- a/Makefile
+++ b/Makefile
@@ -8,7 +8,7 @@
 # Trusted Firmware Version
 #
 VERSION_MAJOR			:= 2
-VERSION_MINOR			:= 11
+VERSION_MINOR			:= 12
 # VERSION_PATCH is only used for LTS releases
 VERSION_PATCH			:= 0
 VERSION				:= ${VERSION_MAJOR}.${VERSION_MINOR}.${VERSION_PATCH}