gpio: sim: add missing fwnode_handle_put() in gpio_sim_probe()

Calling fwnode_handle_put() when break out of device_for_each_child_node(),
or the device node reference will be leakd.

Fixes: 83960fcf4818 ("gpio: sim: new testing module")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>