[VOL-4589] Add interface speed field to openolt proto

Change-Id: I7676a7979a821dc85dc287ae7326737ae8063f6f
diff --git a/protos/voltha_protos/openolt.proto b/protos/voltha_protos/openolt.proto
index 03fe064..bc1883a 100755
--- a/protos/voltha_protos/openolt.proto
+++ b/protos/voltha_protos/openolt.proto
@@ -309,6 +309,7 @@
     string type = 1;		// nni, pon
     fixed32 intf_id = 2;
     string oper_state = 3;      // up, down
+    fixed32 speed = 4;      // measured in Mbps
 }
 
 message OmciIndication {