arm64: dts: rockchip: drop panel port unit address in GRU Scarlet

Panel port does not have "reg", thus it should not have unit address, as
reported by dtc W=1 warning:

  rk3399-gru-scarlet.dtsi:666.32-668.7: Warning (unit_address_vs_reg): /dsi@ff960000/panel@0/ports/port@1/endpoint@1: node has a unit name, but no reg or ranges property

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20240401140939.97808-1-krzk@kernel.org
Signed-off-by: Heiko Stuebner <heiko@sntech.de>