arm64: dts: rockchip: use just "port" in panel on RockPro64

arm64: dts: rockchip: use just "port" in panel on RockPro64

The panel bindings expect to have only one port, thus they do not allow
to use "ports" node:

  rk3399-rockpro64.dtb: panel@0: 'ports' does not match any of the regexes: 'pinctrl-[0-9]+'

There is only one endpoint, so use simpler form without "reg".

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230326204520.80859-3-krzysztof.kozlowski@linaro.org
Signed-off-by: Heiko Stuebner <heiko@sntech.de>