Fix voltha doc for proper voltha upgrade

Change-Id: I8eca2298911f1af26114578fe5d39d7dd8df4a77
diff --git a/charts/voltha.md b/charts/voltha.md
index 16cd2f4..e39a45a 100644
--- a/charts/voltha.md
+++ b/charts/voltha.md
@@ -38,7 +38,7 @@
 resource definition:
 
 ```shell
-helm upgrade voltha ./voltha
+helm upgrade --set etcd-operator.customResources.createEtcdClusterCRD=true voltha ./voltha
 ```
 
 After this first installation, you can use the standard