Add nodes of thermal monitor and thermal zone for UniPhier PXs2 SoC.
The thermal monitor node is included in sysctrl. Since the efuse might not
have a calibrated value of thermal monitor, this patch gives the default
value for PXs2.

Furthermore, add cpuN labels for reference in cooling-device property.
Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>