arm64: dts: mediatek: mt8173 PSCI-1.0 support

This patch adds psci comatible properties to support all mandatory
functions of PSCI-1.0, PSCI-0.2 and PSCI-0.1, and system suspend
can be supported in PSCI-1.0.

Signed-off-by: Fan Chen <fan.chen@mediatek.com>
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>