arm64: dts: uniphier: Add nodes of thermal monitor and thermal zone for PXs3

Add nodes of thermal monitor and thermal zone for UniPhier PXs3 SoC.
The thermal monitor node is included in sysctrl. This patch gives the
default value for PXs3 in the same way as LD20.

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