iio: adc: ad7266: claim direct mode during sensor read

Driver was checking for direct mode but not locking it down.
Use iio_device_claim_direct_mode() to guarantee device stays
in direct mode.
Signed-off-by: Alison Schofield <amsfield22@gmail.com>
Acked-by: Daniel Baluta <daniel.baluta@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/adc/ad7266.c

@@ -154,12 +154,11 @@ static int ad7266_read_raw(struct iio_dev *indio_dev,
 
 	switch (m) {
 	case IIO_CHAN_INFO_RAW:
-		if (iio_buffer_enabled(indio_dev))
-			return -EBUSY;
-
-		ret = ad7266_read_single(st, val, chan->address);
+		ret = iio_device_claim_direct_mode(indio_dev);
 		if (ret)
 			return ret;
+		ret = ad7266_read_single(st, val, chan->address);
+		iio_device_release_direct_mode(indio_dev);
 
 		*val = (*val >> 2) & 0xfff;
 		if (chan->scan_type.sign == 's')