[media] V4L2: sh_mobile_ceu_camera: remove CEU specific data from generic functions

Several functions in the sh_mobile_ceu_camera driver implement generic
algorithms and can be re-used by other V4L2 camera host drivers too. These
functions attempt to optimise scaling and cropping functions of the
subdevice, e.g. a camera sensor. This patch makes those functions generic
for future re-use by other camera host drivers.
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>