[media] adv7842: Deliver resolution change events to userspace

Use the new v4l2_subdev_notify_event() helper function to deliver the
resolution change event to userspace via the v4l2 subdev event queue as
well as to the bridge driver using the callback notify mechanism.

This allows userspace applications to react to changes in resolution. This
is useful and often necessary for video pipelines where there is no direct
1-to-1 relationship between the subdevice converter and the video capture
device and hence it does not make sense to directly forward the event to
the video capture device node.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
[hans.verkuil@cisco.com: fix obvious mistake: v4l2_event_subdev_unsubscribe -> v4l2_ctrl_subdev_subscribe_event]
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>

Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>