Bumping minor versions after VOLTHA-2.7 release

Change-Id: I9acfc611280826f13ec4845f3f2932e1d42571f4
diff --git a/voltha-adapter-openolt/Chart.yaml b/voltha-adapter-openolt/Chart.yaml
index 002985d..fb26816 100644
--- a/voltha-adapter-openolt/Chart.yaml
+++ b/voltha-adapter-openolt/Chart.yaml
@@ -14,7 +14,7 @@
 ---
 apiVersion: "v1"
 name: "voltha-adapter-openolt"
-version: "2.8.8"
+version: "2.9.0-dev"
 description: "A Helm chart for Voltha OpenOLT Adapter"
 keywords:
   - "onf"