NFSv4: When mounting with a port=0 argument, substitute port=2049

RFC3530 states that the registered port 2049 for the NFS protocol should be
the default configuration in order to allow clients not to use the RPC
binding protocols.
If the mount program sends us a port=0, we therefore substitute port=2049.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/super.c

@@ -833,6 +833,9 @@ static int nfs4_get_sb(struct file_system_type *fs_type,
 				__FUNCTION__);
 		return -EINVAL;
 	}
+	/* RFC3530: The default port for NFS is 2049 */
+	if (addr.sin_port == 0)
+		addr.sin_port = NFS_PORT;
 
 	/* Grab the authentication type */
 	authflavour = RPC_AUTH_UNIX;