arm64: dts: mt8192: Add cpu-idle-states

Add idle states for cpu-off and cluster-off.

Signed-off-by: James Liao <jamesjj.liao@mediatek.com>
Link: https://lore.kernel.org/r/20201222045820.26355-1-jamesjj.liao@mediatek.com


Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>