iio: ad5755: fix off-by-one on devnr limit check

The comparison for devnr limits is off-by-one, the current check
allows 0 to AD5755_NUM_CHANNELS and the limit should be in fact
0 to AD5755_NUM_CHANNELS - 1.  This can lead to an out of bounds
write to pdata->dac[devnr]. Fix this by replacing > with >= on the
comparison.
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Fixes: c9474599 ("iio: ad5755: add support for dt bindings")
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/dac/ad5755.c

@@ -655,7 +655,7 @@ static struct ad5755_platform_data *ad5755_parse_dt(struct device *dev)
 
 	devnr = 0;
 	for_each_child_of_node(np, pp) {
-		if (devnr > AD5755_NUM_CHANNELS) {
+		if (devnr >= AD5755_NUM_CHANNELS) {
 			dev_err(dev,
 				"There is to many channels defined in DT\n");
 			goto error_out;