net/mlx4_en: Limit the RFS filter IDs to be < RPS_NO_FILTER

RFS filter id can't have the special value RPS_NO_FILTER,
need to skip it when allocating id's.

CC: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: Amir Vadai <amirv@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>