arm64: dts: mediatek: Introduce MT8192-based Asurada board family

Introduce the MT8192 Asurada Chromebook platform, including the Asurada
Spherion and Asurada Hayato boards.

This is enough configuration to get serial output working on Spherion
and Hayato.

Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Tested-by: Chen-Yu Tsai <wenst@chromium.org>
Link: https://lore.kernel.org/r/20220629155956.1138955-4-nfraprado@collabora.com


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