* Add in the AR724x support. It probes the same as an AR8216/AR8316, so
just add in a hint to force the probe success rather than auto-detecting
it.
* Add in the missing entries from conf/files, lacking in the previous
commit.
The register values and CPU port / mirror port initialisation value was
obtained from Linux OpenWRT ag71xx_ar7240.c.
The DELAY(1000) to let things settle is my local workaround. For some
reason, PHY4 doesn't seem to probe very reliably without it. It's quite
possible that we're missing some MDIO bus initialisation code in if_arge
for the AR724x case. As I dislike DELAY() workarounds in general, it's
definitely worth trying to figure out why this is the case.
Tested on: AP93 (AR7240) reference design
Obtained from: Linux OpenWRT
27a2ecaa9a