arm64: dts: imx8mm: Add empty DSI output endpoint

Also add a corresponding label so overlays can reference that node.
Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8mm.dtsi

@@ -1168,6 +1168,13 @@ dsim_from_lcdif: endpoint {
 							remote-endpoint = <&lcdif_to_dsim>;
 						};
 					};
+
+					port@1 {
+						reg = <1>;
+
+						mipi_dsi_out: endpoint {
+						};
+					};
 				};
 			};