V4L/DVB (10080): soc-camera: readability improvements, more strict operations checks

Simplify multiple drivers by replacing f->fmt.pix.* with a single pointer
dereference, merge some needlessly broken lines, verify host and camera
operations pointers on registration.

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