Calibrate/optimize Semtech SX1278 OOK demodulator

Set frequency and RX channel filter bandwidth (RegRxBw)
Set OokFixedThreshold (RegOokFix, default value: 0xc)
Set continuous mode (RegPacketConfig, bit 6, data processing mode)
Set bit synchronizer off (RegOokPeak, bit 5)

Set DIO mapping
    b = readSPI(RegDioMapping1);
    bitClear(b, 5);
    bitClear(b, 4);
    bitClear(b, 3);
    bitClear(b, 2);
    writeSPI(RegDioMapping1, b);