[media] soc-camera: make .clock_{start,stop} compulsory, .add / .remove optional
[media] soc-camera: make .clock_{start,stop} compulsory, .add / .remove optional

All existing soc-camera host drivers use .clock_start() and .clock_stop()
callbacks to activate and deactivate their camera interfaces, whereas
.add() and .remove() callbacks are usually dummy. Make the former two
compulsory and the latter two optional.

Signed-off-by: Guennadi Liakhovetski <50875182aae23d69ca7738697596f18a14e926fc@gmx.de>
Acked-by: Hans Verkuil <3a513708f73c27e7d36ebc496aa41dad6a3153ea@cisco.com>
Acked-by: Laurent Pinchart <3ded2f39a78f0d7044839546f95841842b4d7c96@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <ad86ba2154032c9f55743a190faa2459a9d61d42@redhat.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs