UV-5RM PLUS frequency limits

[AlphaRne]

I did some rev engineering on the firmware 5RH_NRF_Fangti_V0.14_231124.BF to figure out how to unlock all channels. The external flash location 0xF255 contains a value that sets the limits, with '3' being the most restrictive (ITU1) '5' regular amateur bands and other values fully open.

Here is a little tool that does the job based on the code from the chirp project.

https://github.com/AlphaRne/baofengCtrl