riscv: dts: jh7100: fix soc node compatible

The soc node should only have "simple-bus" in compatible. This matches
what is done for:

  microchip/microchip-mpfs.dtsi
  canaan/k210.dtsi
  sifive/fu740-c000.dtsi

This allows starfive.yaml to pass dt_binding_check without adding:

      - items:
          - const: starfive,jh7100
          - const: simple-bus

Signed-off-by: Drew Fustini <drew@beagleboard.org>

Author: pdp7

arch/riscv/boot/dts/starfive/jh7100.dtsi

@@ -84,7 +84,7 @@
 	};
 
 	soc {
-		compatible = "starfive,jh7100", "simple-bus";
+		compatible = "simple-bus";
 		interrupt-parent = <&plic>;
 		#address-cells = <2>;
 		#size-cells = <2>;