pinctrl: rockchip: Use common interface for recalced iomux

The other Socs also need the feature of recalced iomux, so
make it as a common interface like iomux route feature.

Signed-off-by: David Wu <david.wu@rock-chips.com>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>