Post release increment to version 2.2.0-dev

Change-Id: I85aa57fafc731938b1317b884d611fffbca1b73d
diff --git a/Gopkg.toml b/Gopkg.toml
index 6d1a5ff..a86a5f1 100644
--- a/Gopkg.toml
+++ b/Gopkg.toml
@@ -34,7 +34,7 @@
   version = "1.3.1"
 
 [[constraint]]
-  version = "2.1.0"
+  version = "2.1.1"
   name = "github.com/opencord/voltha-go"
 
 [[constraint]]