e1000e: add ethtool .get_eee/.set_eee

Add the ability to query and set Energy Efficient Ethernet parameters via
ethtool for applicable devices.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Tested-by: Jeff Pieper <jeffrey.e.pieper@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>