This change is for all boards with a sam0 cpu. This cpu just has one ADC.
It is unnecessary to have defines with ADC_0_ prefix as if multiple ADCs
are possible.
Some defines were not used, such as ADC_0_EN, ADC_0_CHANNELS,
ADC_MAX_CHANNELS, ADC_0_CLK_SOURCE, ADC_0_CHANNELS
Change all ADC_0_ prefixes to ADC_
- periph_conf_common.h contains peripherals configuration common to all mkr boards
- periph_conf.h is specific to a subset of mkr boards (mkr1000 and mkrzero)