Use mtk sdk HWNAT driver to replace hw flow offload

[nick008a]

Add OpenWrt support for Xiaomi "Redmi AX6000"

There seem to be a HWNAT (hardware accelerated NAT driver) in the MTK official SDK, and people found that using HWNAT will significantly increase the LAN/WIFI throughput of Redmi AX6000. https://www.right.com.cn/forum/thread-8261104-1-1.html I was trying to compile openwrt snapshot code with the patch, but I am not familiar with kernel development. Maybe someone knows how to upstream this?