dt-bindings: phy: rockchip: convert rockchip-dp-phy.txt to yaml

Convert rockchip-dp-phy.txt to yaml.

Signed-off-by: Johan Jonker <jbx6244@gmail.com>
Acked-By: Vinod Koul <vkoul@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/aa6fe473-71f2-edba-f009-994a3dbc9802@gmail.com


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