[VOL-5129] - Create beta-release branch for voltha-protos

VERSION
-------
  o Bump version string post release and attach a -dev suffix.

Change-Id: Ia49b3777a6dbba2e52d73422dcf425a3cfe803f0
diff --git a/VERSION b/VERSION
index 78e33c5..59feb42 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.12.5.2-dev1
+2.12.5.3-dev