dt-bindings: net: ethernet-controller: drop redundant type from label

dtschema defines label as string, so $ref in other bindings is
redundant.

Signed-off-by: Krzysztof Kozlowski <[e-mail]>
Acked-by: Rob Herring <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

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

···
     pattern: "^ethernet(@.*)?$"
 
   label:
-    $ref: /schemas/types.yaml#/definitions/string
     description: Human readable label on a port of a box.
 
   local-mac-address: