mediatek: filogic: add support for Totolink X6000R

mediatek: filogic: add support for Totolink X6000R

Specification :
- SOC : Mediatek MT7981B (1.3GHz)
- RAM : 256MB
- Flash : 16MB SPI NOR
- Ports : 4 LAN (1G) & 1 WAN (1G)
- WIFI : MediaTek dual-band WiFi 6
  - 2.4 GHz : b/g/n/ax, MIMO 2x2
  - 5 GHz   : a/n/ac/ax, MIMO 2x2
- Buttons : Reset & WPS/Mesh
- LEDS : WAN (Green), Status (Red & Blue)
- Power : 12V1A

Install via OEM web ui:
Upload the sysupgrade image to firmware upgrade page on OEM web ui

Install via recovery / revert to stock firmware:
1. Unplug from power
2. Download the Sysupgrade (for openwrt installation) or OEM Factory image (for revert to stock firmware)
3. Set your computer ethernet IP to 192.168.1.X, subnet 255.255.255.0 (X=your chosen ip number ranging from 2-254)
4. Press and hold reset button while turn on / plug power adapter to the router. Wait untill ALL LAN green LED turn on, then release the reset button.
5. Plug the LAN cable from your computer into LAN 1 port then open web browser, and type in the address column : 192.168.1.1
6. Upload the sysupgrade / oem factory image
7. Wait until the router finished flashing (the router will reboot)
8. Set ethernet ip to dhcp
9. Open 192.168.1.1 (for openwrt install) / 192.168.0.1 (for OEM firmware)

Signed-off-by: Ari Kurniawan <noobhek@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/20035
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>