iio: ad7292: Fix of_node refcounting

When returning or breaking early from a
`for_each_available_child_of_node()` loop, we need to explicitly call
`of_node_put()` on the child node to possibly release the node.

Fixes: 506d2e317a ("iio: adc: Add driver support for AD7292")
Signed-off-by: Nuno Sá <nuno.sa@analog.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20200925091045.302-2-nuno.sa@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/ad7292.c

@@ -310,8 +310,10 @@ static int ad7292_probe(struct spi_device *spi)
 
 	for_each_available_child_of_node(spi->dev.of_node, child) {
 		diff_channels = of_property_read_bool(child, "diff-channels");
-		if (diff_channels)
+		if (diff_channels) {
+			of_node_put(child);
 			break;
+		}
 	}
 
 	if (diff_channels) {