riscv: dts: thead: Add TH1520 AP_SUBSYS clock controller

Add node for the AP_SUBSYS clock controller on the T-Head TH1520 SoC.

Link: https://openbeagle.org/beaglev-ahead/beaglev-ahead/-/blob/main/docs/TH1520%20System%20User%20Manual.pdf
Link: https://git.beagleboard.org/beaglev-ahead/beaglev-ahead/-/tree/main/docs
Signed-off-by: Drew Fustini <dfustini@tenstorrent.com>

arch/riscv/boot/dts/thead/th1520.dtsi

@@ -5,6 +5,7 @@
  */
 
 #include <dt-bindings/interrupt-controller/irq.h>
+#include <dt-bindings/clock/thead,th1520-clk-ap.h>
 
 / {
 	compatible = "thead,th1520";
@@ -419,6 +420,13 @@
 			status = "disabled";
 		};
 
+		clk: clock-controller@ffef010000 {
+			compatible = "thead,th1520-clk-ap";
+			reg = <0xff 0xef010000 0x0 0x1000>;
+			clocks = <&osc>;
+			#clock-cells = <1>;
+		};
+
 		dmac0: dma-controller@ffefc00000 {
 			compatible = "snps,axi-dma-1.01a";
 			reg = <0xff 0xefc00000 0x0 0x1000>;