arm64: dts: mediatek: asurada: Add ChromeOS EC

Add support for the ChromeOS Embedded Controller present on the Asurada
platform. It is connected through the SPI1 bus and offers several
functionalities: base detection, PWM controller, I2C tunneling,
regulators, Type-C connector management, keyboard and Smart Battery
Metrics (SBS).

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/20220629155956.1138955-8-nfraprado@collabora.com


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