arm64: dts: cavium: move non-MMIO node out of soc

Non-MMIO devices, which are BTW not really part of the SoC, should not
be within simple-bus, as reported by dtc W=1 warning:

  thunder-88xx.dtsi:374.28-379.5: Warning (simple_bus_reg): /soc/refclk50mhz: missing or empty reg/ranges property
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20240402194129.69481-1-krzk@kernel.org

arch/arm64/boot/dts/cavium/thunder-88xx.dtsi

@@ -365,12 +365,6 @@ pmu {
 		interrupts = <1 7 4>;
 	};
 
-	soc {
-		compatible = "simple-bus";
-		#address-cells = <2>;
-		#size-cells = <2>;
-		ranges;
-
 	refclk50mhz: refclk50mhz {
 		compatible = "fixed-clock";
 		#clock-cells = <0>;
@@ -378,6 +372,12 @@ refclk50mhz: refclk50mhz {
 		clock-output-names = "refclk50mhz";
 	};
 
+	soc {
+		compatible = "simple-bus";
+		#address-cells = <2>;
+		#size-cells = <2>;
+		ranges;
+
 		gic0: interrupt-controller@8010,00000000 {
 			compatible = "arm,gic-v3";
 			#interrupt-cells = <3>;