doc: fix mountPermissions doc

Author: andyzhangx

docs/driver-parameters.md

@@ -9,7 +9,7 @@ Name | Meaning | Example Value | Mandatory | Default value
 server | NFS Server address | domain name `nfs-server.default.svc.cluster.local` <br>or IP address `127.0.0.1` | Yes |
 share | NFS share path | `/` | Yes |
 subDir | sub directory under nfs share |  | No | if sub directory does not exist, this driver would create a new one
-mountPermissions | mounted folder permissions. The default is `0777`, if set as `0`, driver will not perform `chmod` after mount |  | No |
+mountPermissions | mounted folder permissions. The default is `0`, if set as non-zero, driver will perform `chmod` after mount |  | No |
 
 ### PV/PVC usage (static provisioning)
 > [`PersistentVolume` example](../deploy/example/pv-nfs-csi.yaml)
@@ -18,7 +18,7 @@ Name | Meaning | Example Value | Mandatory | Default value
 --- | --- | --- | --- | ---
 volumeAttributes.server | NFS Server address | domain name `nfs-server.default.svc.cluster.local` <br>or IP address `127.0.0.1` | Yes |
 volumeAttributes.share | NFS share path | `/` |  Yes  |
-volumeAttributes.mountPermissions | mounted folder permissions. The default is `0777` |  | No |
+volumeAttributes.mountPermissions | mounted folder permissions. The default is `0`, if set as non-zero, driver will perform `chmod` after mount |  | No |
 
 ### Tips
 #### `subDir` parameter supports following pv/pvc metadata conversion