staging:iio:impedance-analyser make use of iio_sw_buffer_preenable

This avoids some code duplication by using the generic form
in a non performance critical place.
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Acked-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/iio/impedance-analyzer/ad5933.c

@@ -569,19 +569,14 @@ static const struct iio_info ad5933_info = {
 static int ad5933_ring_preenable(struct iio_dev *indio_dev)
 {
 	struct ad5933_state *st = iio_priv(indio_dev);
-	size_t d_size;
 	int ret;
 
 	if (bitmap_empty(indio_dev->active_scan_mask, indio_dev->masklength))
 		return -EINVAL;
 
-	d_size = bitmap_weight(indio_dev->active_scan_mask,
-			       indio_dev->masklength) *
-		 ad5933_channels[1].scan_type.storagebits / 8;
-
-	if (indio_dev->buffer->access->set_bytes_per_datum)
-		indio_dev->buffer->access->
-			set_bytes_per_datum(indio_dev->buffer, d_size);
+	ret = iio_sw_buffer_preenable(indio_dev);
+	if (ret < 0)
+		return ret;
 
 	ret = ad5933_reset(st);
 	if (ret < 0)