arm64: dts: renesas: rz-smarc-du-adv7513-smarc: Fix missing cells and reg in DU subnode

Add missing cells and reg DT property in the DU subnode to fix the
following DTC W=1 warning:

    arch/arm64/boot/dts/renesas/rz-smarc-du-adv7513.dtsi:29.10-33.5: Warning (unit_address_vs_reg): /fragment@1/__overlay__/ports/port@0: node has a unit name, but no reg or ranges property

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://patch.msgid.link/20260326042411.215241-5-marek.vasut+renesas@mailbox.org
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

Author: Marek Vasut

arch/arm64/boot/dts/renesas/rz-smarc-du-adv7513.dtsi

@@ -26,7 +26,12 @@
 	status = "okay";
 
 	ports {
+		#address-cells = <1>;
+		#size-cells = <0>;
+
 		port@0 {
+			reg = <0>;
+
 			du_out_rgb: endpoint {
 				remote-endpoint = <&adv7513_in>;
 			};