pinctrl/rockchip: Add missing of_node_put() in rockchip_pinctrl_probe

The device_node pointer is returned by of_parse_phandle()  with refcount
incremented. We should use of_node_put() on it when done.

Fixes: 1e747e59 ("pinctrl: rockchip: base regmap supplied by a syscon")
Fixes: 14dee867

 ("pinctrl: rockchip: let pmu registers be supplied by a syscon")
Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
Link: https://lore.kernel.org/r/20220307120234.28657-1-linmq006@gmail.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>