dt-bindings: interrupt-controller: Add Sophgo SG2042 PLIC

Add compatible string for SOPHGO SG2042 plic.
Acked-by: Chao Wei <chao.wei@sophgo.com>
Reviewed-by: Guo Ren <guoren@kernel.org>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Chen Wang <unicorn_wang@outlook.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>

Documentation/devicetree/bindings/interrupt-controller/sifive,plic-1.0.0.yaml

@@ -65,6 +65,7 @@ properties:
       - items:
           - enum:
               - allwinner,sun20i-d1-plic
+              - sophgo,sg2042-plic
               - thead,th1520-plic
           - const: thead,c900-plic
       - items: