ath79: add support for ZiKing CPE46B

ath79: add support for ZiKing CPE46B

ZiKing CPE46B is a POE outdoor 2.4ghz device with an integrated directional
antenna. It is low cost and mostly available via Aliexpress, references can
be found at:
- https://forum.openwrt.org/t/anddear-ziking-cpe46b-ar9331-ap121/60383
- https://git.lsd.cat/g/openwrt-cpe46b

Specifications:

- Atheros AR9330
- 32MB of RAM
- 8MB of flash (SPI NOR)
- 1 * 2.4ghz integrated antenna
- 2 * 10/100/1000 ethernet ports (1 POE)
- 3 * Green LEDs controlled by the SoC
- 3 * Green LEDs controlled via GPIO
- 1 * Reset Button controlled via GPIO
- 1 * 4 pin serial header on the PCB
- Outdoor packaging

Flashing instruction:

You can use sysupgrade image directly in vendor firmware which is based
on OpenWrt/LEDE. In case of issues with the vendor GUI, the vendor
Telnet console is vulnerable to command injection and can be used to gain
a shell directly on the OEM OpenWrt distribution.

Signed-off-by: Giulio Lorenzo <salveenee@mortemale.org>
[fix whitespaces, drop redundant uart status and serial0, drop
num-chipselects, drop 0x1002 MAC address for wmac]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>