docs(changelog): changelog for lts-v2.8.12 release

Generated with the command:
npm run release -- --release-as 2.8.12

Signed-off-by: Yann Gautier <yann.gautier@st.com>
Change-Id: I6accae42ec447cc188616ef37a90cda49f8301c4
diff --git a/Makefile b/Makefile
index ff3b6c4..c7ee8a3 100644
--- a/Makefile
+++ b/Makefile
@@ -9,7 +9,7 @@
 #
 VERSION_MAJOR			:= 2
 VERSION_MINOR			:= 8
-VERSION_PATCH			:= 11
+VERSION_PATCH			:= 12
 VERSION				:= ${VERSION_MAJOR}.${VERSION_MINOR}.${VERSION_PATCH}
 
 # Default goal is build all images