spectrum_flower: Implement gact trap TC action offload

Just use the previously prepared infrastructure and offload the gact
trap action to ACL.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Reviewed-by: Yotam Gigi <yotamg@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>