iio:ad5064: Fix off by one in DAC value range check

The DAC value range check allows values one larger than the maximum value, which
effectively results in setting the DAC value to 0. This patch fixes the issue.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/dac/ad5064.c

@@ -257,7 +257,7 @@ static int ad5064_write_raw(struct iio_dev *indio_dev,
 
 	switch (mask) {
 	case IIO_CHAN_INFO_RAW:
-		if (val > (1 << chan->scan_type.realbits) || val < 0)
+		if (val >= (1 << chan->scan_type.realbits) || val < 0)
 			return -EINVAL;
 
 		mutex_lock(&indio_dev->mlock);