ARM: dts: uniphier: change phy-mode to 'internal' for LD11

Change the phy-mode property to 'internal' that means to use a built-in PHY
implemented on LD11 SoC.

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