dt-bindings: display: rockchip: Add binding for VOP2

The VOP2 is found on newer Rockchip SoCs like the rk3568 or the rk3566.
The binding differs slightly from the existing VOP binding, so add a new
binding file for it.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Reviewed-by: Rob Herring <robh@kernel.org>
Tested-by: Michael Riesch <michael.riesch@wolfvision.net>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20220422072841.2206452-24-s.hauer@pengutronix.de