arm64: dts: uniphier: add reference clock node for PH1-LD20

Add a master clock node generated by a 25MHz crystal oscillator.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

arch/arm64/boot/dts/socionext/uniphier-ph1-ld20.dtsi

@@ -106,6 +106,12 @@ cpu3: cpu@101 {
 	};
 
 	clocks {
+		refclk: ref {
+			compatible = "fixed-clock";
+			#clock-cells = <0>;
+			clock-frequency = <25000000>;
+		};
+
 		uart_clk: uart_clk {
 			#clock-cells = <0>;
 			compatible = "fixed-clock";