dt-bindings: watchdog: apple,wdt: Add t6020-wdt compatible

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

The block on the Apple M2 Pro/Max/Ultra SoCs is compatible with the
existing driver so add its per-SoC compatible.

[1]: https://lore.kernel.org/asahi/12ab93b7-1fc2-4ce0-926e-c8141cfe81bf@kernel.org/

Reviewed-by: Neal Gompa <neal@gompa.dev>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Janne Grunau <j@jannau.net>

Documentation/devicetree/bindings/watchdog/apple,wdt.yaml

@@ -14,8 +14,13 @@ allOf:
 
 properties:
   compatible:
-    items:
+    oneOf:
+      - items:
+          - const: apple,t6020-wdt
+          - const: apple,t8103-wdt
+      - items:
           - enum:
+              # Do not add additional SoC to this list.
               - apple,s5l8960x-wdt
               - apple,t7000-wdt
               - apple,s8000-wdt