staging: iio: ad7606: use iio_device_{claim|release}_direct_mode()

Replace the code that guarantees the device stays in direct mode with
iio_device_{claim|release}_direct_mode() which does same.
Signed-off-by: Alison Schofield <amsfield22@gmail.com>
Acked-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/staging/iio/adc/ad7606_core.c

@@ -88,12 +88,12 @@ static int ad7606_read_raw(struct iio_dev *indio_dev,
 
 	switch (m) {
 	case IIO_CHAN_INFO_RAW:
-		mutex_lock(&indio_dev->mlock);
-		if (iio_buffer_enabled(indio_dev))
-			ret = -EBUSY;
-		else
-			ret = ad7606_scan_direct(indio_dev, chan->address);
-		mutex_unlock(&indio_dev->mlock);
+		ret = iio_device_claim_direct_mode(indio_dev);
+		if (ret)
+			return ret;
+
+		ret = ad7606_scan_direct(indio_dev, chan->address);
+		iio_device_release_direct_mode(indio_dev);
 
 		if (ret < 0)
 			return ret;