docs(changelog): changelog for lts-v2.10.15 release

Change-Id: I389e594db6ea28cde73f1d808aa21b215b5ca541
Signed-off-by: Release CI <ci@trustedfirmware.org>
diff --git a/Makefile b/Makefile
index ff93d9d..fa68215 100644
--- a/Makefile
+++ b/Makefile
@@ -10,7 +10,7 @@
 VERSION_MAJOR			:= 2
 VERSION_MINOR			:= 10
 # VERSION_PATCH is only used for LTS releases
-VERSION_PATCH			:= 14
+VERSION_PATCH			:= 15
 VERSION				:= ${VERSION_MAJOR}.${VERSION_MINOR}.${VERSION_PATCH}
 
 # Default goal is build all images