fix mac address for dual-port 8257[56] cards; ok claudio, kettenis, deraadt
fix mac address for dual-port 8257[56] cards; ok claudio, kettenis, deraadt

orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars