arm64: dts: ulcb: Add DU external dot clock sources

The DU0/DU1/DU2/DU3 external dot clocks are generated by an I2C-controlled
programmable clock generator.

Clock generator is available on both the H3 and M3-W ULCB boards.
Add this to the ulcb.dtsi file.
Signed-off-by: Vladimir Barinov <vladimir.barinov+renesas@cogentembedded.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm64/boot/dts/renesas/ulcb.dtsi

@@ -120,6 +120,12 @@ x12_clk: x12 {
 		#clock-cells = <0>;
 		clock-frequency = <24576000>;
 	};
+
+	x23_clk: x23-clock {
+		compatible = "fixed-clock";
+		#clock-cells = <0>;
+		clock-frequency = <25000000>;
+	};
 };
 
 &audio_clk_a {
@@ -193,6 +199,14 @@ &i2c4 {
 	status = "okay";
 
 	clock-frequency = <400000>;
+
+	versaclock5: clock-generator@6a {
+		compatible = "idt,5p49v5925";
+		reg = <0x6a>;
+		#clock-cells = <1>;
+		clocks = <&x23_clk>;
+		clock-names = "xin";
+	};
 };
 
 &i2c_dvfs {