e1000e: Serdes - attempt autoneg when link restored.

This patch addresses an issue where we did not restart auto-negotiation on
serdes links when the link partner was disabled and re-enabled. It includes
reworking the serdes link detect mechanism to be a state machine for
82571 and 82572 parts only.

Signed-off-by: dave graham <david.graham@intel.com>
Acked-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>