net/mlx4_en: Use the correct netif lock on ndo_set_rx_mode

The device multicast list is protected by netif_addr_lock_bh in the networking core, we should
use this locking practice in mlx4_en too.

Signed-off-by: Eugenia Emantayev <eugenia@mellanox.com>
Signed-off-by: Amir Vadai <amirv@mellanox.com>
Reviewed-by: Yevgeny Petrilin <yevgenyp@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>