The ADC SYNCBUSY.SWTRIG gets stuck to '1' after wake-up from Standby Sleep mode.
Ignore the ADC `SYNCBUSY.SWTRIG` status bit, this functionality is not used by
the driver anyway.
The common ADC API dictates that a sample call must return -1 on an
incorrect resolution. The sam0 ADC implementation instead threw an
assertion failure.
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_
