dt-bindings: display: rockchip: Add schema for RK3588 DW DSI2 controller

The Display Serial Interface 2 (DSI-2) is part of a group of communication
protocols defined by the MIPI Alliance. The RK3588 implements this
specification in its two MIPI DSI-2 Host Controllers that are based on a
new Synopsys IP.

Tested-by: Dmitry Yashin <dmt.yashin@gmail.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Heiko Stuebner <heiko.stuebner@cherry.de>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20241209231021.2180582-3-heiko@sntech.de