gpio: of: add missing of_node_put() in of_gpiochip_scan_gpios()

When terminating for_each_available_child_of_node() iteration
with break or return, of_node_put() should be used to prevent
stale device node references from being left behind.

This is detected by Coccinelle semantic patch.

Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Reviewed-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>