net/mlx4_core: Disable mlx4_QP_ATTACH calls from guests if the host uses flow steering

Guests kernels may not correctly detect if DMFS (device-enabled flow steering) is
activated by the host. If DMFS is activated, the master should return error to guests
which try to use the B0-steering flow calls (mlx4_QP_ATTACH).

Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>