drivers: adc: adc_sam0: Allow all ADC channels to be used

In struct adc_sequence the channels member is a bitset
specifying which channels to cover by the scan.
The sam0 driver only supports one channel to be scanned at a time,
but the check made until now did not regard .channels as a bitset
but a number and thus only accepting a value of 1 aka channel 0

With this fix it is now checked whether more bits are set

Signed-off-by: Kim Bøndergaard <[email protected]>

Author: KimBP

drivers/adc/adc_sam0.c

@@ -392,7 +392,8 @@ static int start_read(const struct device *dev,
 
 	wait_synchronization(adc);
 
-	if (sequence->channels != 1U) {
+	if ((sequence->channels == 0) ||
+		((sequence->channels & (sequence->channels - 1)) != 0)) {
 		LOG_ERR("Channel scanning is not supported");
 		return -ENOTSUP;
 	}