V4L/DVB (8181): gspca: read() did not work (loop in kernel, timeout...)

main:     Remove some vidioc_xx traces.
main:     read() did not work (user irq instead of mmap irq).
main:     Lack of v4l1 compat.
main:     Process loop inside kernel when no frame arriving.
main:     Double qbuf in read() when too many buffered frames.

Signed-off-by: Jean-Francois Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>