igb: add support for 82576NS SerDes adapter

This patch adds the device ID necessary to support the 82576NS SerDes
adapter.

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>