[media] mmp-camera: Don't power up the sensor on resume

We still need to power up the controller to avoid unsightly self-immolation
should something try to access its registers, but the sensor can stay
powered down unless the camera was actually operating at suspend time.
This gets rid of the camera LED flash on resume, fixing OLPC bug #11644.

Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>