periph/adc: add ADC12_B support (FR58xx family)
periph/adc: add ADC12_B support (FR58xx family)

Kinda different beast.  Erratum ADC40 is clearly in evidence; 5% errors
in sampling show up randomly for all voltages.

pabigot/bsp430,pabigot/bsp430,pabigot/bsp430,pabigot/bsp430