arm64: dts: mt8183: kukui: Split out keyboard node and describe detachables

arm64: dts: mt8183: kukui: Split out keyboard node and describe detachables

Kukui devices krane, kodana, and kakadu use detachable keyboards, which
only have switches to be registered.

Change the keyboard node's compatible of those boards to the newly
introduced "google,cros-ec-keyb-switches", which won't include matrix
properties.

Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
Link: https://lore.kernel.org/r/20220527045353.2483042-1-hsinyi@chromium.org
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>