ARM: dts: ls1021a: Add of_graph dt nodes to describe the panel

add of_graph dt nodes to describe the panel, and removed
"fsl,panel" property
Signed-off-by: NMeng Yi <meng.yi@nxp.com>
Acked-by: NStefan Agner <stefan@agner.ch>
Signed-off-by: NShawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/ls1021a-twr.dts

@@ -108,12 +108,23 @@
 
 	panel: panel {
 		compatible = "nec,nl4827hc19-05b";
+
+		port {
+			panel_in: endpoint {
+				remote-endpoint = <&dcu_out>;
+			};
+		};
 	};
 };
 
 &dcu {
-	fsl,panel = <&panel>;
 	status = "okay";
+
+	port {
+		dcu_out: endpoint {
+			remote-endpoint = <&panel_in>;
+		};
+	};
 };
 
 &dspi1 {