arm64: dts: uniphier: add syscon-phy-mode property to each ethernet node

Add syscon-phy-mode property specifying a phandle of system controller
to each ethernet node.

In addition, LD11 SoC has a built-in ethernet PHY. When we set "internal"
to phy-mode property, this built-in PHY is available.
This patch changes phy-mode property for LD11 to "internal", as default.

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