These are needed for some particular port configurations where the default
speed isn't suitable for all link speed types. (Ie, changing 10/100/1000MBit
PLL rate requires a similar MII clock rate, rather than a fixed MII rate.)
This is:
* only currently implemented for the ar71xx;
* isn't used anywhere (yet), as the final interface for this hasn't yet
been determined.
This is untested but should at least allow an AR724X to boot.
The current code is lacking the detail needed to expose the PCIe bus.
It is also lacking any NIC, PLL or flush/WB code.
