dt-bindings: net: renesas: Drop ethernet-phy node schema

What's connected on the MDIO bus is outside the scope of the binding for
ethernet controller's MDIO bus unless it's a fixed internal device, so
drop the node name and reference to ethernet-phy.yaml.

Signed-off-by: Rob Herring <robh@kernel.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20231016-dt-net-cleanups-v1-2-a525a090b444@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>