[Intel-wired-lan] [PATCH v3 1/1] igc: Add initial EEE support

[Andre Guedes]

> IEEE802.3az-2010 Energy Efficient Ethernet has been
> approved as standard (September 2010) and the driver
> can enable and disable it via ethtool.
> Disable the feature by default on parts which support it.
> Add enable/disable eee options.
> tx-lpi, tx-timer and advertise not supported yet.
> 
> v1-v2:
> Rid of inverted logic and replace eee_disable boolean with
> eee_enable in device specification.
> Address community comments.
> 
> v2-v3:
> Remove pointless ret_val from _set_eee method
> Minor comment fix
> 
> Signed-off-by: Sasha Neftin <sasha.neftin at intel.com>

Reviewed-by: Andre Guedes <andre.guedes at intel.com>