ARM: shmobile: lager: Add DU external pixel clocks to DT

Declare the fixed 148.5MHz pixel clocks connected to the DU clock
inputs.
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm/boot/dts/r8a7790-lager.dts

@@ -233,6 +233,18 @@ hdmi_con: endpoint {
 			};
 		};
 	};
+
+	x2_clk: x2-clock {
+		compatible = "fixed-clock";
+		#clock-cells = <0>;
+		clock-frequency = <148500000>;
+	};
+
+	x13_clk: x13-clock {
+		compatible = "fixed-clock";
+		#clock-cells = <0>;
+		clock-frequency = <148500000>;
+	};
 };
 
 &du {
@@ -240,6 +252,15 @@ &du {
 	pinctrl-names = "default";
 	status = "okay";
 
+	clocks = <&mstp7_clks R8A7790_CLK_DU0>,
+		 <&mstp7_clks R8A7790_CLK_DU1>,
+		 <&mstp7_clks R8A7790_CLK_DU2>,
+		 <&mstp7_clks R8A7790_CLK_LVDS0>,
+		 <&mstp7_clks R8A7790_CLK_LVDS1>,
+		 <&x13_clk>, <&x2_clk>;
+	clock-names = "du.0", "du.1", "du.2", "lvds.0", "lvds.1",
+		      "dclkin.0", "dclkin.1";
+
 	ports {
 		port@0 {
 			endpoint {