ARM: dts: add clock support for Airoha EN7523

This driver only registers fixed rate clocks, since the clocks are fully
initialized by the boot loader and should not be changed later, according
to Airoha.

Signed-off-by: Felix Fietkau <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Matthias Brugger <[e-mail]>

arch/arm/boot/dts/en7523.dtsi

···
 #include <dt-bindings/interrupt-controller/irq.h>
 #include <dt-bindings/interrupt-controller/arm-gic.h>
 #include <dt-bindings/gpio/gpio.h>
+#include <dt-bindings/clock/en7523-clk.h>
 
 / {
 	interrupt-parent = <&gic>;
···
 		L2_0: l2-cache0 {
 			compatible = "cache";
 		};
+	};
+
+	scu: system-controller@1fa20000 {
+		compatible = "airoha,en7523-scu";
+		reg = <0x1fa20000 0x400>,
+		      <0x1fb00000 0x1000>;
+		#clock-cells = <1>;
 	};
 
 	gic: interrupt-controller@9000000 {