ARM: shmobile: marzen: Add DU external pixel clock to DT

Declare the fixed 65MHz pixel clock connected to the DU clock input.
Signed-off-by: NLaurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: NSimon Horman <horms+renesas@verge.net.au>

arch/arm/boot/dts/r8a7779-marzen.dts

@@ -122,6 +122,12 @@
 			};
 		};
 	};
+
+	x3_clk: x3-clock {
+		compatible = "fixed-clock";
+		#clock-cells = <0>;
+		clock-frequency = <65000000>;
+	};
 };
 
 &du {
@@ -129,6 +135,9 @@
 	pinctrl-names = "default";
 	status = "okay";
 
+	clocks = <&mstp1_clks R8A7779_CLK_DU>, <&x3_clk>;
+	clock-names = "du", "dclkin.0";
+
 	ports {
 		port@0 {
 			endpoint {