[media] V4L: soc-camera: remove now unused soc-camera specific PM hooks

soc-camera host drivers shall be implementing their PM, using standard
kernel methods, soc-camera specific hooks can die.

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