don't read/write 1000baseT specific MII registers on 10/100M ony device. From dragonflybsd
don't read/write 1000baseT specific MII registers on 10/100M ony device.
From dragonflybsd

tested by krw@

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