iio: adc: cc10001_adc: make use of iio_for_each_active_channel()

Use iio_for_each_active_channel() to iterate over active channels
accessing '.masklength' so it can be annotated as __private when there are
no more direct users of it.
Signed-off-by: Nuno Sa <nuno.sa@analog.com>
Link: https://patch.msgid.link/20240718-dev-iio-masklength-private2-v1-1-8e12cd042906@analog.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/cc10001_adc.c

@@ -157,9 +157,7 @@ static irqreturn_t cc10001_adc_trigger_h(int irq, void *p)
 
 	i = 0;
 	sample_invalid = false;
-	for_each_set_bit(scan_idx, indio_dev->active_scan_mask,
-				  indio_dev->masklength) {
-
+	iio_for_each_active_channel(indio_dev, scan_idx) {
 		channel = indio_dev->channels[scan_idx].channel;
 		cc10001_adc_start(adc_dev, channel);