dt-bindings: display: rockchip: Convert cdn-dp-rockchip.txt to yaml

dt-bindings: display: rockchip: Convert cdn-dp-rockchip.txt to yaml

Convert cdn-dp-rockchip.txt to yaml.

Add new "port@1" property which represents the CDN DP output to keep
the same style as the other display interfaces.

This patch also changes the constraints for "phys" and "extcon". For
the original binding, only one phy and the corresponding extcon can
be specified. In the new binding, one or two phys can be specified.
Since the RK3399 has two DP-USB PHYs, specifying one allows output
via the corresponding PHY, while specifying two lets the driver
choose one PHY for output. This rule also applies to extcon, which
provides the cable state for the corresponding PHY.

Signed-off-by: Chaoyi Chen <chaoyi.chen@rock-chips.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20250520024718.142-3-kernel@airkyi.com
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>