re: Leverage Realtek driver's chip/PHY initialization/reset.

re: Leverage Realtek driver's chip/PHY initialization/reset.

It is mainly used to solve all kinds of weirdness, e.g. hanging after
watchdog timeout, and PHY read failure, we have encountered so far on
these chips.

The DEVMETHODs, ifnet setup, and data path are still ours.  miibus(4)
is no longer used, ifmedia(4) is used directly.

NOTE: This change drops the 8139C+ and 8169 w/ external PHY support,
which are deemed to be too old.

Realtek's driver is taken from their website: version 1.92 (2016/10/25).

Tested-by: dillon, zrj