e1000e: clear PHY wakeup bit after LCD reset on 82577/82578

Performing a dummy read of the PHY Wakeup Control (WUC) register clears the
wakeup enable bit set by an PHY reset.  If this bit remains set, link
problems may occur.

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>