pinctrl: mediatek: Fix missing of_node_put() in mtk_pctrl_init

pinctrl: mediatek: Fix missing of_node_put() in mtk_pctrl_init

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

Fixes: a6df410d420a ("pinctrl: mediatek: Add Pinctrl/GPIO driver for mt8135.")
Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20220308071155.21114-1-linmq006@gmail.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>