iio: adc: ad7791: Switch to sparse friendly iio_device_claim/release_direct()

These new functions allow sparse to find failures to release
direct mode reducing chances of bugs over the claim_direct_mode()
functions that are deprecated

Reviewed-by: Nuno Sá <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/adc/ad7791.c

···
 {
 	int ret;
 
-	ret = iio_device_claim_direct_mode(indio_dev);
-	if (ret)
-		return ret;
+	if (!iio_device_claim_direct(indio_dev))
+		return -EBUSY;
 
 	ret = __ad7791_write_raw(indio_dev, chan, val, val2, mask);
 
-	iio_device_release_direct_mode(indio_dev);
+	iio_device_release_direct(indio_dev);
 	return ret;
 }