iio: adc: stm32-adc: make use of iio_get_masklength()

Use iio_get_masklength() to access '.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/20240726-dev-iio-masklength-private3-v1-8-82913fc0fb87@analog.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/stm32-adc.c

@@ -1261,7 +1261,7 @@ static int stm32_adc_conf_scan_seq(struct iio_dev *indio_dev,
 	stm32_adc_writel(adc, adc->cfg->regs->smpr[0], adc->smpr_val[0]);
 	stm32_adc_writel(adc, adc->cfg->regs->smpr[1], adc->smpr_val[1]);
 
-	for_each_set_bit(bit, scan_mask, indio_dev->masklength) {
+	for_each_set_bit(bit, scan_mask, iio_get_masklength(indio_dev)) {
 		chan = indio_dev->channels + bit;
 		/*
 		 * Assign one channel per SQ entry in regular
@@ -1619,7 +1619,7 @@ static int stm32_adc_update_scan_mode(struct iio_dev *indio_dev,
 	if (ret < 0)
 		return ret;
 
-	adc->num_conv = bitmap_weight(scan_mask, indio_dev->masklength);
+	adc->num_conv = bitmap_weight(scan_mask, iio_get_masklength(indio_dev));
 
 	ret = stm32_adc_conf_scan_seq(indio_dev, scan_mask);
 	pm_runtime_mark_last_busy(dev);