The ioctl entry point, a big switch/case, is splitted in little 
functions. 

These functions are set as callbacks for the video_ioctl2 video4linux 
facility.

This improves the driver memory consumption and enables the v4l1 
compatibility as a side effect.
Signed-off-by: NThierry MERLE <thierry.merle@free.fr>
Acked-by: NDwaine P. Garden <dwainegarden@rogers.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@infradead.org>