ramips: add support for Wavlink WS-WN572HP3 4G

ramips: add support for Wavlink WS-WN572HP3 4G

Wavlink WS-WN572HP3 4G is an 802.11ac
dual-band outdoor router with LTE support.

Specifications;
* Soc: MT7621DAT
* RAM: 128MiB
* Flash: NOR 16MiB GD-25Q128ESIG3
* Wi-Fi:
  * MT7613BEN: 5GHz
  * MT7603EN: 2.4GHz
* Ethernet: 2x 1GbE
* USB: None - only used internally
* LTE Modem: Quectel EC200T-EU
* UART: 115200 baud
* LEDs:
  * 7 blue at the front
    * 1 Power
    * 2 LAN / WAN
    * 1 Status
    * 3 RSSI (annotated 4G)
  * 1 green at the bottom (4G LED)
* Buttons: 1 reset button

Installation:
* press and hold the reset button while powering on the device
* keep it pressed for ten seconds
* connect to 192.168.10.1 via webbrowser (chromium/chrome works, at
  least Firefox 106.0.3 does not)
* upload the sysupgrade image, confirm the checksum, wait 2 minutes
  until the device reboots

Revert to stock firmware:
* same as installation but use the recovery image for WL-WN572HP3

Signed-off-by: Jan-Niklas Burfeind <git@aiyionpri.me>
Acked-by: Arınç ÜNAL <arinc.unal@arinc9.com>