VOL-3735 Retrieve port counters using the GetExtValue(SingleGetValue) rpc from the openolt adapter

Change-Id: Ie7cd02b6a5b3784d7cc279a616ce88d4ee89ef20
diff --git a/vendor/modules.txt b/vendor/modules.txt
index 69107ad..f5769bf 100644
--- a/vendor/modules.txt
+++ b/vendor/modules.txt
@@ -104,9 +104,10 @@
 github.com/modern-go/concurrent
 # github.com/modern-go/reflect2 v1.0.1
 github.com/modern-go/reflect2
-# github.com/opencord/voltha-protos/v4 v4.0.6
+# github.com/opencord/voltha-protos/v4 v4.0.8
 github.com/opencord/voltha-protos/v4/go/common
 github.com/opencord/voltha-protos/v4/go/ext/config
+github.com/opencord/voltha-protos/v4/go/extension
 github.com/opencord/voltha-protos/v4/go/inter_container
 github.com/opencord/voltha-protos/v4/go/omci
 github.com/opencord/voltha-protos/v4/go/openflow_13