mediatek: filogic: add support for Cudy AP3000 Wall v1

mediatek: filogic: add support for Cudy AP3000 Wall v1

This commit adds support for the Cudy AP3000 Wall v1.

SoC: MediaTek MT7981b
RAM: 256MiB
Flash: spi-nand spi0.0: 128 MiB
Wifi: MediaTek MT7981 2x2 DBDC 802.11ax 2T2R (2.4 / 5)
LEDs: 1 LED in two colors (red & white)
Buttons: 1 reset, 1 led on/off
Ethernet: 5x 1GbE
Power: PoE powered (standalone)

The stock firmware is a customized variant of OpenWrt, which implements
a signature check that only allows flashing official firmware. Cudy offers
intermediate OpenWrt firmware images on their website [1][2] which do not
implement the signature check. After flashing the intermediate image the
upstream official OpenWrt image can be installed.

The stock firmware can be recovered via TFTP using the U-Boot based boot
loader[3]. Set up a TFTP server on your computer with IP 192.168.1.88/24
serving the stock firmware from Cudy's website renamed to "recovery.bin".
Press and hold the reset button while powering on the device, wait for the
TFTP server to send the recovery.bin file, then release the reset button.
The router will take a couple of minutes to reboot and set up the stock
firmware.

[1] https://www.cudy.com/blogs/faq/openwrt-software-download
[2] https://drive.google.com/drive/folders/1BKVarlwlNxf7uJUtRhuMGUqeCa5KpMnj
[3] https://www.cudy.com/en-us/blogs/faq/how-to-recovery-the-cudy-router-from-openwrt-firmware-to-cudy-official-firmware

Signed-off-by: Derek Denk <derek.denk@live.com>
Link: https://github.com/openwrt/openwrt/pull/21266
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>