i40e: Change unknown event error msg to ignore message

There's no real error in an unknown event from the Firmware, we're just
posting a useful FYI notice, so this patch simply removes the "Error" word.

Signed-off-by: Shannon Nelson <shannon.nelson@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>