Update omci-lib-go to 2.2.0 and use new ME attribute constants instead of strings

Change-Id: If0bee47bede5e02c70f73c6c615bafc55d1389d5
diff --git a/go.mod b/go.mod
index 36c1a57..964a90e 100644
--- a/go.mod
+++ b/go.mod
@@ -23,7 +23,7 @@
 	github.com/olekukonko/tablewriter v0.0.4
 	github.com/opencord/cordctl v0.0.0-20190909161711-01e9c1f04bf4
 	github.com/opencord/device-management-interface v1.2.1
-	github.com/opencord/omci-lib-go/v2 v2.1.2
+	github.com/opencord/omci-lib-go/v2 v2.2.0
 	github.com/opencord/voltha-protos/v5 v5.1.2
 	github.com/pkg/errors v0.8.1 // indirect
 	github.com/sirupsen/logrus v1.4.2