dt-bindings: net: ethernet-controller: Rework 'fixed-link' schema

While the if/then schemas mostly work, there's a few issues. The 'allOf'
schema will also be true if 'fixed-link' is not an array or object as a
false 'if' schema (without an 'else') will be true. In the array case
doesn't set the type (uint32-array) in the 'then' clause. In the node case,
'additionalProperties' is missing.

Rework the schema to use oneOf with each possible type.
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/ethernet-controller.yaml

@@ -167,10 +167,8 @@ properties:
       - in-band-status
 
   fixed-link:
-    allOf:
-      - if:
-          type: array
-        then:
+    oneOf:
+      - $ref: /schemas/types.yaml#/definitions/uint32-array
         deprecated: true
         items:
           - minimum: 0
@@ -196,11 +194,8 @@ properties:
             description:
               Asymmetric pause configuration. 0 for no asymmetric
               pause, 1 for asymmetric pause
-
-
-      - if:
-          type: object
-        then:
+      - type: object
+        additionalProperties: false
         properties:
           speed:
             description: