Upgrade: Longhorn from 1.5.2 to 1.6.4

Change-Id: I8cdc3c0a07133f00442b496800ccc30e2c1dad61
diff --git a/charts/longhorn/Chart.yaml b/charts/longhorn/Chart.yaml
index 1609eb5..04e57cc 100644
--- a/charts/longhorn/Chart.yaml
+++ b/charts/longhorn/Chart.yaml
@@ -1,5 +1,5 @@
 apiVersion: v1
-appVersion: v1.5.2
+appVersion: v1.6.4
 description: Longhorn is a distributed block storage system for Kubernetes.
 home: https://github.com/longhorn/longhorn
 icon: https://raw.githubusercontent.com/cncf/artwork/master/projects/longhorn/icon/color/longhorn-icon-color.png
@@ -25,4 +25,4 @@
 - https://github.com/longhorn/longhorn-ui
 - https://github.com/longhorn/longhorn-tests
 - https://github.com/longhorn/backing-image-manager
-version: 1.5.2
+version: 1.6.4