pinctrl: rockchip: Add set_config callback support for gpiolib

Could only support PIN_CONFIG_INPUT_DEBOUNCE now as the HW block
is too simple to support others. But even wrt. debounce capability,
it now could only support very limited period of time to satisfy the
real usecase. But still be useful to enable the crippled HW debounce
to prevent any spurious glitches from waking up the system if the
gpio is conguired as wakeup interrupt source.

Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>