e1000e: ensure the link state is correct for serdes links

This patch ensures that the link state (as reported in
mac->serdes_has_link) will transition to false when autoneg fails to
complete but valid codewords were detected.

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>