V4L/DVB (12535): soc-camera: remove .init() and .release() methods from struct soc_camera_ops

Remove unneeded soc-camera operations, this also makes the soc-camera API to
v4l2 subdevices thinner.

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