iio: health: max30102: 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/20240718-dev-iio-masklength-private2-v1-6-8e12cd042906@analog.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/health/max30102.c

@@ -293,7 +293,7 @@ static irqreturn_t max30102_interrupt_handler(int irq, void *private)
 	struct iio_dev *indio_dev = private;
 	struct max30102_data *data = iio_priv(indio_dev);
 	unsigned int measurements = bitmap_weight(indio_dev->active_scan_mask,
-						  indio_dev->masklength);
+						  iio_get_masklength(indio_dev));
 	int ret, cnt = 0;
 
 	mutex_lock(&data->lock);