[VOL-4080] Extend GetExtValue api to read transceiver rx-power on demand.

Change-Id: I2916b83e859977ee57282c8a4fffad7926ce9861
diff --git a/go.mod b/go.mod
index f3e6a6b..7397871 100644
--- a/go.mod
+++ b/go.mod
@@ -10,7 +10,7 @@
 	github.com/jessevdk/go-flags v1.4.0
 	github.com/jhump/protoreflect v1.5.0
 	github.com/opencord/voltha-lib-go/v4 v4.3.0
-	github.com/opencord/voltha-protos/v4 v4.1.7
+	github.com/opencord/voltha-protos/v4 v4.1.8
 	github.com/stretchr/testify v1.4.0
 	go.etcd.io/etcd v0.0.0-20190930204107-236ac2a90522
 	golang.org/x/oauth2 v0.0.0-20190604053449-0f29369cfe45 // indirect