iio: imu: bno055: 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-v1-10-8e12cd042906@analog.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/imu/bno055/bno055.c

@@ -1458,7 +1458,7 @@ static irqreturn_t bno055_trigger_handler(int irq, void *p)
 	 * then we split the transfer, skipping the gap.
 	 */
 	for_each_set_bitrange(start, end, iio_dev->active_scan_mask,
-			      iio_dev->masklength) {
+			      iio_get_masklength(iio_dev)) {
 		/*
 		 * First transfer will start from the beginning of the first
 		 * ones-field in the bitmap