pinctrl: rockchip: Add rk3506 pinctrl support

Add support for the 5 rk3506 GPIO banks.

Signed-off-by: Ye Zhang <ye.zhang@rock-chips.com>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Author: Ye Zhang