net: mlx4: slight optimization of addr compare

Use possibly more efficient ether_addr_equal
to instead of memcmp.

Cc: Amir Vadai <amirv@mellanox.com>
Signed-off-by: Ding Tianhong <dingtianhong@huawei.com>
Acked-By: Amir Vadai <amirv@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>