igb: Copyright string update to year 2013

This patch updates Copyright year to 2013

v2: Changed Copyright year on Makefile

Signed-off-by: Akeem G. Abodunrin <akeem.g.abodunrin@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>