mlx4_en: Removing HW info from ethtool -i report.

Avoiding abuse of ethtool_drvinfo.driver field.
HW specific info can be retrieved using lspci.

Signed-off-by: Yevgeny Petrilin <yevgenyp@mellanox.co.il>
Signed-off-by: David S. Miller <davem@davemloft.net>