media: iris: implement subscribe_event and unsubscribe_event ioctls

media: iris: implement subscribe_event and unsubscribe_event ioctls

Implement the subscribe_event and unsubscribe_event iocts with the
necessary hooks.

Signed-off-by: Vedang Nagar <quic_vnagar@quicinc.com>
Reviewed-by: Hans Verkuil <hverkuil@xs4all.nl>
Tested-by: Stefan Schmidt <stefan.schmidt@linaro.org> # x1e80100 (Dell XPS 13 9345)
Reviewed-by: Stefan Schmidt <stefan.schmidt@linaro.org>
Tested-by: Neil Armstrong <neil.armstrong@linaro.org> # on SM8550-QRD
Tested-by: Neil Armstrong <neil.armstrong@linaro.org> # on SM8550-HDK
Signed-off-by: Dikshita Agarwal <quic_dikshita@quicinc.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>