docs(changelog): changelog for v2.7 release

Change-Id: I573e5eb3c7fad097892292c8a967dc02d72d12e6
Signed-off-by: Jayanth Dodderi Chidanand <jayanthdodderi.chidanand@arm.com>
diff --git a/Makefile b/Makefile
index 05d97b0..8d55ab9 100644
--- a/Makefile
+++ b/Makefile
@@ -8,7 +8,7 @@
 # Trusted Firmware Version
 #
 VERSION_MAJOR			:= 2
-VERSION_MINOR			:= 6
+VERSION_MINOR			:= 7
 
 # Default goal is build all images
 .DEFAULT_GOAL			:= all