pinctrl: rockchip: only enable gpio clock when it setting

gpio can keep state even the clock disable, for save power
consumption, only enable gpio clock when it setting

Signed-off-by: Lin Huang <hl@rock-chips.com>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Tested-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>