[VOL-3107] Add DeleteGroup API in openolt.proto

Change-Id: I6aa82e364f4b37a02e45e2e09ce10f2042ffd9fa
diff --git a/protos/voltha_protos/openolt.proto b/protos/voltha_protos/openolt.proto
index 13d7a38..fea6ebc 100644
--- a/protos/voltha_protos/openolt.proto
+++ b/protos/voltha_protos/openolt.proto
@@ -174,6 +174,13 @@
         };
     }
 
+    rpc DeleteGroup(Group) returns (Empty) {
+        option (google.api.http) = {
+          post: "/v1/DeleteGroup"
+          body: "*"
+        };
+    }
+
     rpc GetExtValue(ValueParam) returns (common.ReturnValues) {
         option (google.api.http) = {
           post: "/v1/GetExtValue"