Use flow_rule_is_supp_control_flags()

Check the mask, not the key, for unsupported control flags.

Only compile-tested, no access to HW
Signed-off-by: Asbjørn Sloth Tønnesen <ast@fiberby.net>
Reviewed-by: Louis Peens <louis.peens@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>