Add support for Xiaomi Redmi Ax5400 (white version)

For Developers
44

anything new about this router

45

IPQ50xx support exists - https://downloads.openwrt.org/snapshots/targets/qualcommax/ipq50xx/, but there's no open PR for the AX5400.

46

this router is supportable, but we need someone who owns the device willing to make a start and we can help along the way.. the hardware is probably similar to the Redmi AX3000 with a beefier QCN9024 (4x4) instead of QCN6122 (2x2) 5G wifi chip.

@hzyitc has built an image for it already here:
hzyitc/openwrt-redmi-ax3000: Openwrt for Redmi AX3000 / Xiaomi CR880x / Xiaomi CR881x

47

I have the router, let me know what to do help.