ARM: dts: rockchip: fix graph node unit address error from dtc

The updated dtc emits a warning for the edp-panel of two rk3288 boards:
    Warning (graph_endpoint): /dp@ff970000/ports/port@1/endpoint: graph node unit address error, expected "0"

Fix this by adding the necessary @0 to the endpoint node.
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm/boot/dts/rk3288-evb.dtsi

@@ -232,7 +232,7 @@ edp_out: port@1 {
 			#address-cells = <1>;
 			#size-cells = <0>;
 
-			edp_out_panel: endpoint {
+			edp_out_panel: endpoint@0 {
 				reg = <0>;
 				remote-endpoint = <&panel_in_edp>;
 			};

arch/arm/boot/dts/rk3288-veyron-chromebook.dtsi

@@ -174,7 +174,7 @@ edp_out: port@1 {
 			reg = <1>;
 			#address-cells = <1>;
 			#size-cells = <0>;
-			edp_out_panel: endpoint {
+			edp_out_panel: endpoint@0 {
 				reg = <0>;
 				remote-endpoint = <&panel_in_edp>;
 			};