ath79: Port PowerCloud Systems CAP324 support

ath79: Port PowerCloud Systems CAP324 support

The CAP324 was an AP for a NaaS offering that is now defunct.  While
previously supported in the ar71xx arch, there were some errata (to
be fixed shortly).

Notable differences from ar71xx support:

1) The method of getting the ath9k firmware for the PCIe 2ghz wifi has
changed (due to changes in how the arch handles this), since this device
doesn't use the EEPROM except to get the MAC address of the wifi.

2) /etc/config/wireless will need to be regenerated as the path(s) to
the wireless device(s) have changed.

3) ath79 OpenWrt firmware no longer supports build an image that allows
reverting to stock firmware (as the cloud service no longer exists, the
stock firmware is useless), instead using all of the flash for image and
overlay (less u-boot/env and art).

4) Initial network config treats the ethernet port as a Lan port with
the standard default address (192.168.1.1 unless changed in .config
--e.g. via menuconfig) instead of using DHCP (this was the default for
the stock firmware, however for openwrt use this is rather confusion and
counter-productive as the user has a harder time finding the device on
the network.

Signed-off-by: Daniel F. Dickinson <cshored@thecshore.com>