ath79-generic: add support for D-Link DAP-2695

[s-2]

split from #3190

The DAP-2695 (better late than never) is an AC1750 Wave 1 Access Point in a plenum-rated metal case with RJ45 serial console port and six detachable antennas (single band, labelled accordingly).

DAP-2695 Specifications:
* SoC: Qualcomm Atheros QCA9558, 256 MiB RAM, 16 MiB SPI NOR
* Ethernet: 2x 10/100/1000 (1x 802.3at PoE-PD)
* WiFi 2.4GHz: Qualcomm Atheros QCA9558
* WiFi 5GHz: Qualcomm Ahteros QCA9880-2R4E
* LEDS: 1x 5GHz, 1x 2.4GHz, 1x LAN1(POE), 1x LAN2, 1x POWER
* UART: 1x RJ45 RS-232 Console port
* Plenum-rated metal case

https://hannover.freifunk.net/karte/#!/de/map/9cd6432cac70
https://hannover.freifunk.net/karte/#!/de/map/0cb6d2fd1570

Checklist (Tested for DAP-2695 A1 and A2)

• Must be flashable from vendor firmware
  • Web interface
  • [-] TFTP
  • Other: recovery webinterface (keep reset button pressed during power-on, until upload started)
• Must support upgrade mechanism
  • Must have working sysupgrade
    • Must keep/forget configuration (sysupgrade [-n], firstboot)
  • Gluon profile name matches autoupdater image name
    (lua -e 'print(require("platform_info").get_image_name())')
• Reset/WPS/... button must return device into config mode
• Primary MAC address should match address on device label (or packaging)
  (https://gluon.readthedocs.io/en/latest/dev/hardware.html#notes)
  • 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
  • should support all network ports on the device
  • must have correct port assignment (WAN/LAN)
    • On devices supplied via PoE, there is usually no explicit WAN/LAN labeling on the hardware.
      The PoE input should be the WAN port in this case.
• Wireless network (if applicable)
  • Association with AP must be possible on all radios
  • Association with 802.11s mesh must work on all radios
  • AP+mesh mode must work in parallel on all radios
• LED mapping
  • Power/system LED
    • Lit while the device is on
    • Should display config mode blink sequence
      (https://gluon.readthedocs.io/en/latest/features/configmode.html)
  • Radio LEDs
    • Should map to their respective radio
    • Should show activity
  • Switch port LEDs
    • Should map to their respective port (or switch, if only one led present)
    • Should show link state and activity
• Outdoor devices only:
  • [-] Added board name to is_outdoor_device function in package/gluon-core/luasrc/usr/lib/lua/gluon/platform.lua

[blocktrron]

Needs rebase