ramips: add support for TP-Link Archer AX23 v1

ramips: add support for TP-Link Archer AX23 v1

Hardware
--------
CPU:    MediaTek MT7621 DAT
RAM:    128MB DDR3 (integrated)
FLASH:  16MB SPI-NOR ()
WiFi:   MediaTek MT7905 + MT7975 (2.4 / 5 DBDC) 802.11ax
SERIAL: 115200 8N1
        LEDs - (3V3 - GND - RX - TX) - ETH ports

Installation
------------

Upload the factory image using the Web-UI.

Web-Recovery
------------

The router supports a HTTP recovery mode by holding the reset-button
when powering on. The interface is reachable at 192.168.0.1 and supports
installation using the factory image.

Signed-off-by: David Bauer <mail@david-bauer.net>
(cherry picked from commit 7dceef5ee554ec4ab5d2dd2ff999f4a60bf2e0f4)