Additional serial protocol: Graupner HoTT SUMD (#2137)
* initial commit
* editorial changes
* removed unnecessary extern definitions and include
* forgotten items
* don't occupy RX if SUMD (as in SBUS)
setting SUMD Failsafe bit is not necessary as it is handled by !frameAvailable
* CRC: changed from using crc table to polynomial calculation
plus some editorial changes
* follwing @pkendall64's review:
- removed not necessary changes
- moved defines to .cpp file
* following @Jye's review changed crc calculation to use existing ExpressLRS class