Releasing 5.1.6 for voltha-2.5

Change-Id: I285a335374dc34dd3c6408c1aeb5a546d3d13664
diff --git a/VERSION b/VERSION
index 24fadfe..8710cfd 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-5.1.6-dev
+5.1.6