dt-bindings: rockchip: Add Rockchip rk3566 box demo board

Add device tree binding for Rockchip rk3566 box demo board.

Signed-off-by: Andy Yan <andyshrk@163.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20221105095935.958144-1-andyshrk@163.com


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