Bumping voltha core chart

Change-Id: I6d4acc47e50d362cda06944875f2d85c20d7eefa
diff --git a/.gitreview b/.gitreview
index 2b11b97..243818c 100644
--- a/.gitreview
+++ b/.gitreview
@@ -3,3 +3,4 @@
 port=29418
 project=voltha-helm-charts.git
 defaultremote=origin
+defaultbranch=voltha-2.5