igb: Enable the hardware traffic class feature bit for igb models

This will allow functionality depending on the hardware being traffic
class aware to work. In particular the tc-flower offloading checks
verifies that this bit is set.

Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>