ramips-mt76x8: add RE200 version 4

[misanthropos]

• [x] Must be flashable from vendor firmware

  • [x] Web interface
  • [x] TFTP

• [x] Must support upgrade mechanism

  • [x] Must have working sysupgrade
  • [x] Must keep/forget configuration (sysupgrade [-n], firstboot)
  • [x] Gluon profile name matches autoupdater image name (lua -e 'print(require("platform_info").get_image_name())')

• [x] Reset/WPS/... button must return device into config mode

• [x] Primary MAC address should match address on device label (or packaging) (https://gluon.readthedocs.io/en/latest/dev/hardware.html#hardware-support-in-packages)

  • When re-adding a device that was supported by an earlier version of Gluon, a factory reset must be performed before checking the primary MAC address, as the setting from the old version is not reset otherwise.

• Wired network

  • [x] should support all network ports on the device
  • [x] must have correct port assignment (WAN/LAN)
  • if there are multiple ports but no WAN port:
    • the PoE input should be WAN, all other ports LAN
    • otherwise the first port should be declared as WAN, all other ports LAN

• Wireless network (if applicable)

  • [x] Association with AP must be possible on all radios
  • [x] Association with 802.11s mesh must work on all radios
  • [x] AP+mesh mode must work in parallel on all radios

• LED mapping

  • Power/system LED
  • [x] Lit while the device is on
  • [x] Should display config mode blink sequence (https://gluon.readthedocs.io/en/latest/features/configmode.html)
  • Radio LEDs
  • [x] Should map to their respective radio
  • [x] Should show activity
  • Switch port LEDs
  • [x] Should map to their respective port (or switch, if only one led present)
  • [x] Should show link state and activity
  • [x] Added Device to docs/user/supported_devices.rst

[maurerle]

For completeness: related PR #2347 tried to introduce support as well and did mention some issues. The issues were fixed in upstream openwrt https://github.com/openwrt/openwrt/issues/11855 And are said to be resolved now (also mentioned in gluon IRC).