dt-bindings: mediatek: Add optional mediatek,gce-events property

This property is used by gce clients.

Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210622030741.2120393-2-hsinyi@chromium.org


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