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

Change-Id: If6201799946ac753780d0424c4bd986e2fb394d2
diff --git a/rw_core/mocks/adapter_onu.go b/rw_core/mocks/adapter_onu.go
index 549e016..5f4a5e6 100644
--- a/rw_core/mocks/adapter_onu.go
+++ b/rw_core/mocks/adapter_onu.go
@@ -18,6 +18,7 @@
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"strings"
 	"sync"
@@ -240,3 +241,10 @@
 
 	onuA.flows = map[uint64]*voltha.OfpFlowStats{}
 }
+
+func (onuA *ONUAdapter) 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")
+}