pinctrl: rockchip: Use devm_pinctrl_register() for pinctrl registration

Use devm_pinctrl_register() for pin control registration.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Cc: Heiko Stuebner <heiko@sntech.de>
Cc: linux-rockchip@lists.infradead.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>