mediatek: filogic: Add support ASUS RT-AX57M

mediatek: filogic: Add support ASUS RT-AX57M

ASUS RT-AX57M, RT-AX54HP V2, RT-AX1800HP V2, RT-AX1800S V2, and RT-AX3000S all use the same firmware and have identical hardware

Hardware
--------
SOC: MediaTek MT7981b
RAM: 256MB DDR3L (Winbond W632GU6NB-09)
FLASH: 128MB SPI-NAND (Winbond W25N01KVZEIR)
WIFI: Mediatek MT7981b + Mediatek MT7976DAN 802.11ax 2.4/5 GHz
ETH: MediaTek MT7531AE Switch
UART: 3V3 115200 8N1 (Pinout silkscreened / Do not connect VCC)

MAC addresses
-------------
LAN	Label MAC (stored in mtd ubi Factory partition at offset 0x4)
WAN	LAN
2.4G	LAN + 2 in first octet
5G	LAN

Installation
-----------------------------------------------------------
Vendor-UI Method
-----------------------------------------------------------
1. Download the OpenWrt initramfs.trx image.

2. Connect the PC via LAN to one of the yellow router ports and wait
   until your PC to get a DHCP lease.

3. Browse to http://192.168.1.1 (or whatever your router IP is configured as)

4. If your router is brand new, finish the setup process and log into
   the Web-UI.

5. Navigate to Administration -> Firmware Upgrade and upload the
   downloaded OpenWrt initramfs.trx image.

6. Wait for OpenWrt to boot. Open the default OpenWrt IP in a web browser and perform a system upgrade using the sysupgrade image as instructed in the top banner.

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Revert to stock firmware:
1: Install package facinstall -> https://forum.openwrt.org/t/facinstall-package-for-easy-installation-factory-images/177587
2. Install Asus stock trx image via OpenWRT LuCI interface.

Signed-off-by: Garrett Mesmer <garrettmesm@gmail.com>
Co-authored-by: Oleg S <remittor@gmail.com>
Signed-off-by: Oleg S <remittor@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/20491
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>