Add support for Xiaomi AX1800 Wifi 6 router

[Gingernut]

Didn't see it mentioned but the exact same process to gain permanent ssh/telnet access and be able to permanently change the router's CountryCode for the AX3600 works perfectly on the AX1800 with the same crash_unlock.img and instructions.

Download the crash_unlock.img file from here:

Xiaomi ax3600 ssh guide

Finally managed to get a different crash_unlock.img file from https://www.wutaijie.cn/?p=254, which is really got the mtd partition writable. I completed all the rest of the steps, but instead of having ssh permanently even the existing one is disappeared. After upgrade to the miwifi_r3600_firmware_f7f3e_1.0.67 firmware telnet is working, so then I was able to turn turn back ssh!!! All the files collected for this or other methods are here:

Follow this guide:

AX3600 永久开启telnet-ssh