ARM: dts: am57xx: compulab-sb-som: add HDMI connector

Add HDMI connector node without a valid input endpoint.

CompuLab SB-SOM is a carrier board, hence the endpoint
should be added in the board DT with a valid HDMI output.

Signed-off-by: Dmitry Lifshitz <[e-mail]>
Acked-by: Igor Grinberg <[e-mail]>
Signed-off-by: Tony Lindgren <[e-mail]>

arch/arm/boot/dts/compulab-sb-som.dtsi

···
 			pixelclk-active = <1>;
 		};
 	};
+
+	hdmi_conn: connector@0 {
+		compatible = "hdmi-connector";
+		label = "hdmi";
+
+		type = "a";
+	};
 };