DMR FLC RS(12,9) - Reimplement Algorithm

[DSheirer]

The current RS(12,9) code is using the Reed Solomon decoder and it's not functioning correctly for this application. DMR uses a shortened RS code. This is for the FLC carried in the Voice Header.

Also, in this sample there are no bit errors detected during BPTC extraction for the Voice SuperFrame FLC, but on reassembly it has a zero valued checksum when it should be 0x11. Trace the checksum bits back through processing and extraction to see if we're not picking up the checksum correctly.

See bitstream recording from @wedgef5 for invalid CRC checks on Voice Header FLC messages.
File: 20250108_074124_155422500_9600BPS_DMR_Crawford_County_Public_Safety_Frontenac_CH2_4.bits
Stored on T9: /recordings/DMR/wedgef5...