igb: make certain to power on optics for 82576 fiber nics

It appears that a step was missed in the initialization of 82576 fiber nics
that resulted in it not powering on the optics.

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>