ceph: wrong pool name for CephFS StorageClass

* This error is found in creating CephFS StorageClass using document `Documentation/ceph-csi-drivers.md`: "expect a pool named `cephfs_data` in your Ceph cluster"
* **`kubectl apply -f pool.yaml` using metadata.name "cephfs_data" produce error:** The CephBlockPool "cephfs_data" is invalid: metadata.name: Invalid value: "cephfs_data": a DNS-1123 subdomain must consist of lower case alphanumeric characters, '-' or '.', and must start and end with an alphanumeric character (e.g. 'example.com', regex used for validation is '[a-z0-9]([-a-z0-9]*[a-z0-9])?(\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*')
* accoding to `Documentation/ceph-filesystem-crd.md` linked from `Documentation/ceph-csi-drivers.md` file and field test, it should be `myfs-data0`

Signed-off-by: Joel Huang <joelhy@gmail.com>

Documentation/ceph-csi-drivers.md

@@ -360,7 +360,7 @@ kubectl delete -f cluster/examples/kubernetes/ceph/csi/example/rbd/storageclass.
 
 This
 [storageclass](../cluster/examples/kubernetes/ceph/csi/example/cephfs/storageclass.yaml)
-expect a pool named `cephfs_data` in your Ceph cluster. You can create this
+expect a pool named `myfs-data0` in your Ceph cluster. You can create this
 pool using [rook file-system
 CRD](https://github.com/rook/rook/blob/master/Documentation/ceph-filesystem-crd.md).
 

cluster/examples/kubernetes/ceph/csi/example/cephfs/storageclass.yaml

@@ -12,7 +12,7 @@ parameters:
 
   # Ceph pool into which the volume shall be created
   # Required for provisionVolume: "true"
-  pool: cephfs_data
+  pool: myfs-data0
 
   # Root path of an existing CephFS volume
   # Required for provisionVolume: "false"