arm64: dts: rockchip: add an input enable pinconf to rk3399

Add a pinconf to configure pins as input-enable.

Signed-off-by: Caleb Connolly <kc@postmarketos.org>
Link: https://lore.kernel.org/r/20220328005005.72492-5-kc@postmarketos.org


Signed-off-by: Heiko Stuebner <heiko@sntech.de>