ARM: dts: rockchip: convert pinctrl nodes to new bindings

Introduce the grf syscon and convert the pinctrl drivers for rk3066 and rk3188
to use it, instead of mapping the grf registers themselfs.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Tested-by: Max Schwarz <max.schwarz@online.de>
Acked-by: Linus Walleij <linus.walleij@linaro.org>