Energy Efficient Ethernet on 82579 and I217 should only be enabled if not
disabled by the user, if the link is full duplex and the link partner has
similar EEE capabilities (stored in different EMI registers on the two
different parts).

After enabling EEE, read the IEEE MMD register 3.1 (which is also stored in
different EMI registers on the two different parts) to clear the count of
received Tx/Rx LPI indications.

Also, rename I217_EEE_100_SUPPORTED to I82579_EEE_100_SUPPORTED to indicate
the bit is valid starting with I82579 (released before I217).
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>