net/mlx4_en: Add interface identify support

Add support for the interface ethtool identify feature.

Make the physical port LED to blink with green and yellow colors.

The device handles the LED blink by itself (synchrous use of
set_phys_id), by returning 0 to ETHTOOL_ID_ACTIVE command.

Signed-off-by: Eyal Grossman <eyalgr@mellanox.com>
Signed-off-by: Ido Shamay <idos@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>