[VOL-4741] openonuAdapterGo: Make OMCI message set support configurable

Change-Id: Ieef80c7aca1dfc3481c11a0c0a153cfa9212ba20
diff --git a/voltha-adapter-openonu/values.yaml b/voltha-adapter-openonu/values.yaml
index 374e857..c2c6cac 100644
--- a/voltha-adapter-openonu/values.yaml
+++ b/voltha-adapter-openonu/values.yaml
@@ -48,6 +48,9 @@
   # Configure Performance Metrics
   metrics:
     enabled: true
+  # Configure Extended OMCI Support
+  extended_omci_support:
+    enabled: false
   # Configure Mib Audit
   mib_audit:
   # configure "0s" to disable Mib Audit