dt-bindings: net: ave: Use unevaluatedProperties

This refers common bindings, so this is preferred for
unevaluatedProperties instead of additionalProperties.

Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>