soc: amlogic: meson-pwrc: Hold reference returned by of_get_parent()

We should hold the reference returned by of_get_parent() and use
it to call of_node_put() for refcount balance.

Signed-off-by: Liang He <windhl@126.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://lore.kernel.org/r/20220726073841.1320509-1-windhl@126.com