NFS4: Set parsed mount data version to 4

This patch only affects mounting through "-t nfs4" since it doesn't set
up an nfs version to use in the mount data.  The nfs client was trying
to mount using NFS v0, causing either a BUG() or a protocol not
supported message.
Signed-off-by: Bryan Schumaker <bjschuma@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/super.c

@@ -2637,6 +2637,8 @@ static int nfs4_validate_mount_data(void *options,
 	if (data == NULL)
 		goto out_no_data;
 
+	args->version = 4;
+
 	switch (data->version) {
 	case 1:
 		if (data->host_addrlen > sizeof(args->nfs_server.address))