ARM: dts: uniphier: Rename ethphy node to ethernet-phy

This renames the node name "ethphy" to "ethernet-phy" according to
Documentation/devicetree/bindings/net/mdio.yaml.

Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>