of_get_parent() will return a device_node pointer with refcount
incremented. We need to use of_node_put() on it when done. Add the
missing of_node_put() in the error path of berlin2_adc_probe();

Fixes: 70f19379 ("iio: adc: add support for Berlin")
Signed-off-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Link: https://lore.kernel.org/r/20221129020316.191731-1-wangxiongfeng2@huawei.com
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>