pinctrl: rockchip: Add common rockchip pinctrl driver

Use this driver to fit all Rockchip SOCs and to support
the desired pinctrl configuration via DTS.

Signed-off-by: David Wu <david.wu@rock-chips.com>
Acked-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>