iio: proximity: hx9023s: 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-v1-20-8e12cd042906@analog.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/proximity/hx9023s.c

@@ -936,7 +936,7 @@ static irqreturn_t hx9023s_trigger_handler(int irq, void *private)
 		goto out;
 	}
 
-	for_each_set_bit(bit, indio_dev->active_scan_mask, indio_dev->masklength) {
+	iio_for_each_active_channel(indio_dev, bit) {
 		index = indio_dev->channels[bit].channel;
 		data->buffer.channels[i++] = cpu_to_le16(data->ch_data[index].diff);
 	}
@@ -957,7 +957,7 @@ static int hx9023s_buffer_preenable(struct iio_dev *indio_dev)
 	unsigned int bit;
 
 	guard(mutex)(&data->mutex);
-	for_each_set_bit(bit, indio_dev->active_scan_mask, indio_dev->masklength)
+	iio_for_each_active_channel(indio_dev, bit)
 		__set_bit(indio_dev->channels[bit].channel, &channels);
 
 	hx9023s_update_chan_en(data, channels, data->chan_event);