V4L/DVB (8629): v4l2-ioctl: do not try to handle private V4L1 ioctls

Some drivers (e.g. zoran) have private V4L1 ioctls. Do not try to
pass them to v4l1_compat_translate because then the driver will
never see them.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>