Use openolt adapter version 2.5.6

Change-Id: Ieac293a6f7fdbf26dcfcc057b0af157bda3eb260
diff --git a/voltha-adapter-openolt/Chart.yaml b/voltha-adapter-openolt/Chart.yaml
index 1947456..ae48b1a 100644
--- a/voltha-adapter-openolt/Chart.yaml
+++ b/voltha-adapter-openolt/Chart.yaml
@@ -14,7 +14,7 @@
 ---
 apiVersion: "v1"
 name: "voltha-adapter-openolt"
-version: "2.6.2"
+version: "2.6.4"
 description: "A Helm chart for Voltha OpenOLT Adapter"
 keywords:
   - "onf"
@@ -33,4 +33,4 @@
 
 # appVersion refers to multiple components with potentially different
 # container image versions.
-appVersion: "2.5.5"
+appVersion: "2.5.6"