igc: Remove obsolete IGC_ERR define

Address community comment.
Remove obsolete IGC_ERR define and use dev_err method.
Suggested by Joe Perches.

Signed-off-by: Sasha Neftin <sasha.neftin@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>