i40e: fix mac address checking

Remove custom i40e functions around ethernet addresses that are
duplicating already existing kernel functionality.

Also ends up fixing a bug with multicast addresses.

Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Kavindya Deegala <kavindya.s.deegala@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>