V4L/DVB (6735): Reorder functions to make easier to compare with the previous code

After this patch, the order of the functions will be the same as before the
patch converting the driver to user video_ioctl2. This makes easier to diff
between the previous version and the newer one.

Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>