arm64: dts: mt8173: Add afe device node

This adds afe (audio front end) device node to the MT8173 dtsi file.

Signed-off-by: Koro Chen <koro.chen@mediatek.com>
Reviewed-by: Daniel Kurtz <djkurtz@chromium.org>
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>