dt-bindings: soc: fsl: add missed compatible string fsl,ls*-isc

Add compatible string, fsl,ls1088a-isc, fsl,ls2080a-isc, fsl,lx2160a-isc.
Fix the below warning:
arch/arm64/boot/dts/freescale/fsl-ls2080a-qds.dtb: /soc/syscon@1f70000: failed to match any schema with compatible: ['fsl,ls2080a-isc', 'syscon']
Signed-off-by: Frank Li <Frank.Li@nxp.com>
Link: https://lore.kernel.org/r/20240806162121.2996442-1-Frank.Li@nxp.comSigned-off-by: Rob Herring (Arm) <robh@kernel.org>

Documentation/devicetree/bindings/soc/fsl/fsl,layerscape-scfg.yaml

@@ -23,6 +23,9 @@ properties:
           - fsl,ls1028a-scfg
           - fsl,ls1043a-scfg
           - fsl,ls1046a-scfg
+          - fsl,ls1088a-isc
+          - fsl,ls2080a-isc
+          - fsl,lx2160a-isc
       - const: syscon
 
   reg: