mediatek: add support for reyee AX3200-E5

mediatek: add support for reyee AX3200-E5

This is yet another model of the Ruijie RG-EW3200GX PRO with a slightly
different flash layout, install process is the same.

Specifications:
SoC: MT7622B
RAM: 256MB
Flash: XMC XM25QH128C or Winbond WQ25Q128JVSQ 16MB SPI NOR
Ethernet: 5x1GbE
Switch: MT7531BE
WiFi: 2.4G: MT7622 5G: MT7915AN+MT7975AN
3LEDs: System LED(blue) + Mesh LED(green) + Mesh LED(red)
2Keys: Mesh button + Reset button
UART: Marked J19 on board. 3.3v, 115200n1
Power: 12V 2.5A

Flash instruction:
1. Serve the initramfs.img using a TFTP server with address 10.10.10.3.
2. Interrupt the uboot startup process via UART.
3. Select "System Load Linux to SDRAM via TFTP" item.
4. (important) Back up firmware(mtd7) partitions with:
    dd if=/dev/mtd7 of=/tmp/firmware.bin
    and then download the firmware.bin image via SCP.
5. Flash the OpenWrt sysupgrade firmware.

Recovery stock firmware:

1. Transfer the firmware.bin image to the device.
2. Flash the image with:
    mtd write firmware.bin firmware

Signed-off-by: Alex Hansen <mralexh123@gmail.com>
Signed-off-by: Daniel Golle <daniel@makrotopia.org>