arm64: dts: mt8173: Add thermal zone node.

This adds thermal zone node to Mediatek MT8173 dtsi file.

Signed-off-by: Dawei Chien <dawei.chien@mediatek.com>
Acked-by: Eduardo Valentin <edubezval@gmail.com>
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>