ARM: dts: exynos: Move fixed clocks under root node in Exynos3250

The fixed clocks are kept under dedicated node fixed-rate-clocks, thus a
fake "reg" was added.  This is not correct with dtschema as fixed-clock
binding does not have a "reg" property:

  arch/arm/boot/dts/exynos3250-artik5-eval.dt.yaml: clock@0: 'reg' does not match any of the regexes: 'pinctrl-[0-9]+'
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Link: https://lore.kernel.org/r/20200829172532.29358-2-krzk@kernel.org

arch/arm/boot/dts/exynos3250.dtsi

@@ -97,33 +97,25 @@ cpu1: cpu@1 {
 		};
 	};
 
-	fixed-rate-clocks {
-		#address-cells = <1>;
-		#size-cells = <0>;
-
-		xusbxti: clock@0 {
-			compatible = "fixed-clock";
-			reg = <0>;
-			clock-frequency = <0>;
-			#clock-cells = <0>;
-			clock-output-names = "xusbxti";
-		};
+	xusbxti: clock-0 {
+		compatible = "fixed-clock";
+		clock-frequency = <0>;
+		#clock-cells = <0>;
+		clock-output-names = "xusbxti";
+	};
 
-		xxti: clock@1 {
-			compatible = "fixed-clock";
-			reg = <1>;
-			clock-frequency = <0>;
-			#clock-cells = <0>;
-			clock-output-names = "xxti";
-		};
+	xxti: clock-1 {
+		compatible = "fixed-clock";
+		clock-frequency = <0>;
+		#clock-cells = <0>;
+		clock-output-names = "xxti";
+	};
 
-		xtcxo: clock@2 {
-			compatible = "fixed-clock";
-			reg = <2>;
-			clock-frequency = <0>;
-			#clock-cells = <0>;
-			clock-output-names = "xtcxo";
-		};
+	xtcxo: clock-2 {
+		compatible = "fixed-clock";
+		clock-frequency = <0>;
+		#clock-cells = <0>;
+		clock-output-names = "xtcxo";
 	};
 
 	pmu {