Update gitreview for v2.11 to merge with branch voltha-2.11 by default

Change-Id: I55489d764a4d8a742a00fb80c85a5eb21fa5422a
diff --git a/.gitreview b/.gitreview
index c70a26b..b4e51b8 100644
--- a/.gitreview
+++ b/.gitreview
@@ -3,3 +3,4 @@
 port=29418
 project=voltha-go.git
 defaultremote=origin
+defaultbranch=voltha-2.11