arm64: dts: realtek: Add oscillator for RTD129x

Add 27 MHz oscillator clock node.
Signed-off-by: Andreas Färber <afaerber@suse.de>

arch/arm64/boot/dts/realtek/rtd129x.dtsi

@@ -23,6 +23,13 @@ arm_pmu: arm-pmu {
 		interrupts = <GIC_SPI 48 IRQ_TYPE_LEVEL_HIGH>;
 	};
 
+	osc27M: osc {
+		compatible = "fixed-clock";
+		clock-frequency = <27000000>;
+		#clock-cells = <0>;
+		clock-output-names = "osc27M";
+	};
+
 	soc {
 		compatible = "simple-bus";
 		#address-cells = <1>;