ramips: add support for I-O DATA WN-AX2033GR2

ramips: add support for I-O DATA WN-AX2033GR2

I-O DATA WN-AX2033GR2 is roughly the same as I-O DATA WN-AX2033GR.
The difference is the Flash Memory (Macronix MX30LF1G18AC).

Specification
=============
- SoC: MediaTek MT7621A
- RAM: DDR3 128 MiB
- Flash Memory: NAND 128 MiB (Macronix MX30LF1G18AC)
- Wi-Fi: MediaTek MT7603E
- Wi-Fi: MediaTek MT7615
- Ethernet: 5x 10 Mbps / 100 Mbps / 1000 Mbps (1x WAN, 4x LAN)
- LED: 2x green LED
- Input: 2x tactile switch, 1x slide switch
- Power: DC 12V

Flash instruction
=================
1. Open the router management page (192.168.0.1).
2. Update router firmware using "initramfs-kernel.bin".
3. After updating, run sysupgrade with "sysupgrade.bin".

Signed-off-by: Hiroki Utsunomiya <hu-git-ja@proton.me>
Link: https://github.com/openwrt/openwrt/pull/22762
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>