arm64: dts: rockchip: add core devicetree for rk3326

The rk3326 is basically a px30 without the second display controller.
So add a dtsi based on that, that just removes the affected nodes.

Signed-off-by: Heiko Stuebner <heiko.stuebner@theobroma-systems.com>
Link: https://lore.kernel.org/r/20200414082938.2977572-1-heiko@sntech.de


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