[VOL-3196] Using the latest voltha-lib-go in the openolt adapter

Change-Id: I0c6d166f3dda8e9cca9e19a2f33aeee96a8cc6c3
diff --git a/VERSION b/VERSION
index 9080d9c..73462a5 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.5.1-dev
+2.5.1