V4L/DVB (10074): soc-camera: add camera sense data

Add a struct soc_camera_sense, that can be used by camera host drivers to
request additional information from a camera driver, for example, when
changing data format. This struct can be extended in the future, its first use
is to request the camera driver whether the pixel-clock frequency has changed.

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