e1000e: disable K1 at 1000Mbps for 82577/82578

This workaround is required for an issue in hardware where noise on the
interconnect between the MAC and PHY could be generated by a lower power
mode (K1) at 1000Mbps resulting in bad packets.  Disable K1 while at 1000
Mbps but keep it enabled for 10/100Mbps and when the cable is disconnected.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>