gpio/rockchip: fix refcount leak in rockchip_gpiolib_register()

In the Linux kernel, the following vulnerability has been resolved: gpio/rockchip: fix refcount leak in rockchip_gpiolib_register() The node returned by of_get_parent() with refcount incremented, of_node_put() needs be called when finish using it. So add it in the end of of_pinctrl_get().