dt-bindings: arm: Add bindings for Mediatek MT8183 SoC Platform

This adds dt-binding documentation of cpu for Mediatek MT8183.

Signed-off-by: Erin Lo <erin.lo@mediatek.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>