[VOL-936] add changes for onu distance from OLT

Change-Id: If6201799946ac753780d0424c4bd986e2fb394d2
diff --git a/rw_core/mocks/adapter_olt.go b/rw_core/mocks/adapter_olt.go
index 5f67da7..07077c8 100644
--- a/rw_core/mocks/adapter_olt.go
+++ b/rw_core/mocks/adapter_olt.go
@@ -332,3 +332,10 @@
 
 	oltA.flows = map[uint64]*voltha.OfpFlowStats{}
 }
+
+func (oltA *OLTAdapter) Get_ext_value(deviceId string, device *voltha.Device, valueflag voltha.ValueType_Type) (*voltha.ReturnValues, error) { // nolint
+	_ = deviceId
+	_ = device
+	_ = valueflag
+	return nil, errors.New("get-ext-value-not-implemented")
+}