[media] v4l: vsp1: Setup control handler automatically at stream on time

[media] v4l: vsp1: Setup control handler automatically at stream on time

When setting a control directly on a subdev node the VSP1 driver doesn't
guarantee that the device is powered on. This leads to crashes when the
control handlers writes to hardware registers. One easy way to fix this
is to ensure that the device gets powered on when a subdev node is
opened. However, this consumes power unnecessarily, as there's no need
to power the device on when setting formats on the pipeline.
Furthermore, control handler setup at entity init time suffers from the
same problem as the device isn't powered on easier.

Fix this by extend the entity base object to setup the control handler
automatically when starting the stream. Entities must then skip writing
to registers in the set control handler when not streaming, which can be
tested with the new vsp1_entity_is_streaming() helper function.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>