arm64: dts: rockchip: Enable RS232 for edgeble-neu6b

Add RS232 support for Edgeble Neu6B NCM IO board.
Signed-off-by: Jagan Teki <jagan@edgeble.ai>
Link: https://lore.kernel.org/r/20230713143941.1756849-7-jagan@edgeble.aiSigned-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm64/boot/dts/rockchip/rk3588-edgeble-neu6b-io.dts

@@ -77,3 +77,10 @@ &uart2 {
 	pinctrl-0 = <&uart2m0_xfer>;
 	status = "okay";
 };
+
+/* RS232 */
+&uart6 {
+	pinctrl-0 = <&uart6m0_xfer>;
+	pinctrl-names = "default";
+	status = "okay";
+};