spectrum: flower: Treat ETH_P_ALL as a special case and translate for HW

HW does not understand ETH_P_ALL. So treat this special case differently
and translate to 0/0 key/mask. That will allow HW to match all ethertypes.

Fixes: 7aa0f5aa

 ("mlxsw: spectrum: Implement TC flower offload")
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>