iio: adc: hx711: 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-v1-3-8e12cd042906@analog.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/hx711.c

@@ -363,10 +363,7 @@ static irqreturn_t hx711_trigger(int irq, void *p)
 
 	memset(hx711_data->buffer, 0, sizeof(hx711_data->buffer));
 
-	for (i = 0; i < indio_dev->masklength; i++) {
-		if (!test_bit(i, indio_dev->active_scan_mask))
-			continue;
-
+	iio_for_each_active_channel(indio_dev, i) {
 		hx711_data->buffer[j] = hx711_reset_read(hx711_data,
 					indio_dev->channels[i].channel);
 		j++;