net/mlx4_en: Don't reassign port mac address on firmware that supports it

Mac reassignments should only be done when not supported by the firmware. To
accomplish that, checking firmware capability bit to know whether we should
reassign macs in the driver.

Signed-off-by: Matan Barak <matanb@mellanox.com>
Signed-off-by: Amir Vadai <amirv@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>