gpio: rockchip: Call pinctrl for gpio config

Pinctrl is responsible for bias settings and possibly other pin config,
so call gpiochip_generic_config to apply such config values. This might
also include settings that pinctrl does not support, but then it can
return ENOTSUPP as appropriate.

Signed-off-by: Matthijs Kooijman <matthijs@stdin.nl>
Signed-off-by: Linus Walleij <linusw@kernel.org>