[media] soc-camera: Push probe-time power management to drivers

Several client drivers access the hardware at probe time, for instance
to read the probe chip ID. Such chips need to be powered up when being
probed.

soc-camera handles this by powering chips up in the soc-camera probe
implementation. However, this will break with non soc-camera hosts that
don't perform the same operations.

Fix the problem by pushing the power up/down from the soc-camera core
down to individual drivers on a needs basis.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>