Release voltha-go master branch version 2.2.0

Change-Id: Ifd64ff7aa50c29a3b272bd00234b0206629aa8b9
diff --git a/python/adapters/ponsim_olt/VERSION b/python/adapters/ponsim_olt/VERSION
index 97ade15..ccbccc3 100644
--- a/python/adapters/ponsim_olt/VERSION
+++ b/python/adapters/ponsim_olt/VERSION
@@ -1 +1 @@
-2.2.0-dev
+2.2.0