dt-bindings: clock: apple,nco: Add t6020-nco compatible

After discussion with the devicetree maintainers we agreed to not extend
lists with the generic compatible "apple,nco" anymore [1]. Use
"apple,t8103-nco" as base compatible as it is the SoC the driver and
bindings were written for.

The block found on Apple's M2 Pro/Max/Ultra SoCs is compatible with
"apple,t8103-nco" so add its per-SoC compatible with the former as
fallback used by the existing driver.

[1]: https://lore.kernel.org/asahi/[e-mail]/

Reviewed-by: Neal Gompa <[e-mail]>
Acked-by: Rob Herring (Arm) <[e-mail]>
Signed-off-by: Janne Grunau <[e-mail]>

Documentation/devicetree/bindings/clock/apple,nco.yaml

···
 
 properties:
   compatible:
-    items:
-      - enum:
-          - apple,t6000-nco
-          - apple,t8103-nco
-          - apple,t8112-nco
-      - const: apple,nco
+    oneOf:
+      - items:
+          - const: apple,t6020-nco
+          - const: apple,t8103-nco
+      - items:
+          - enum:
+              # Do not add additional SoC to this list.
+              - apple,t6000-nco
+              - apple,t8103-nco
+              - apple,t8112-nco
+          - const: apple,nco
 
   clocks:
     description: