[media] sh_mobile_ceu_camera: implement the control handler

And since this is the last and only host driver that uses controls, also
remove the now obsolete control fields from soc_camera.h.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
[g.liakhovetski@gmx.de: moved code around, fixed problems]
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>