Reduce the delays a bit in the miibus read/write routines.
Reduce the delays a bit in the miibus read/write routines.

Although with aditional 20us delays added just before returning
from miibus read/writes as required by the hardware.

Based on the Linux r8169 driver; from Brad.

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