[VOL-5009] - Update release notes

release_notes/voltha_2.12.rst
-----------------------------
  o Import Mahir(s) word doc containing tickets and descriptions.
  o Reformat using a grid layout so tickets and description are aligned.

Change-Id: Ic8ca17f5923496731f88ce8918c9852d904ea066
diff --git a/VERSION b/VERSION
index c815807..419a356 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.12.6-dev
+2.12.6-dev1