arm64: dts: mt8183: add cbas node under cros_ec

Add a 'cbas' device node for supporting tablet mode switch in
kukui devices.

Kukui platforms with detacheable base have an additional input
device under cros-ec, which reports SW_TABLET_MODE regarding
its base state (e.g. base flipped or detached).

Signed-off-by: Ikjoon Jang <ikjn@chromium.org>
Reviewed-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>

Link: https://lore.kernel.org/r/20210609032554.2443675-1-ikjn@chromium.org


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