igb: do not force pcs link when in KX mode

We were forcing the PCS link up in error when we are in KX mode.  We should
only be disabling autoneg, not forcing the link up.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>