iio:ad7887: Remove redundant call to iio_sw_buffer_preenable().

The equivalent of iio_sw_buffer_preenable() is now done in the IIO buffer core,
so there is no need to do this from the driver anymore.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/adc/ad7887.c

@@ -78,11 +78,6 @@ enum ad7887_supported_device_ids {
 static int ad7887_ring_preenable(struct iio_dev *indio_dev)
 {
 	struct ad7887_state *st = iio_priv(indio_dev);
-	int ret;
-
-	ret = iio_sw_buffer_preenable(indio_dev);
-	if (ret < 0)
-		return ret;
 
 	/* We know this is a single long so can 'cheat' */
 	switch (*indio_dev->active_scan_mask) {