Update device capabilities regarding HW filtering multicast loopback support.

Add MLX4_UPDATE_QP_ETH_SRC_CHECK_MC_LB attribute to mlx4_update_qp to
enable changing QP context to support filtering incoming multicast
loopback traffic according the sender's counter index.

Set the corresponding bits in QP context to force the loopback source
checks if attribute is given and HW supports it.
Signed-off-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Eran Ben Elisha <eranbe@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>