arm64: dts: rockchip: Enable DisplayPort for rk3588s Cool Pi 4B

arm64: dts: rockchip: Enable DisplayPort for rk3588s Cool Pi 4B

Enable the Mini DisplayPort on this board.
Note that ROCKCHIP_VOP2_EP_DP0 is defined as 10 in dt-binding header,
but it will trigger a dtc warning like "graph node unit address error,
expected "a"" if we use it directly after endpoint, so we use "a"
instead here.

Signed-off-by: Andy Yan <andy.yan@rock-chips.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20250822063959.692098-10-andyshrk@163.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>