iio: dac: ad7303: remove an unneeded check

"ret" is zero here.  There is no need to check again.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/dac/ad7303.c

@@ -92,7 +92,7 @@ static ssize_t ad7303_write_dac_powerdown(struct iio_dev *indio_dev,
 	ad7303_write(st, chan->channel, st->dac_cache[chan->channel]);
 
 	mutex_unlock(&indio_dev->mlock);
-	return ret ? ret : len;
+	return len;
 }
 
 static int ad7303_get_vref(struct ad7303_state *st,