V4L/DVB (9790): soc-camera: pixel format negotiation - core support

Allocate and fill a list of formats, supported by this specific
camera-host combination. Use it for format enumeration. Take care to stay
backwards-compatible.

Camera hosts rely on sensor formats available, as well as
host specific translations. We add a structure so that hosts
can define a translation table and use it for format check
and setup.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>