V4L/DVB: Don't access input_dev->private directly

Drivers should use input_{get|set}_drvdata() instead of accessing
input_dev->provate directly, but since these drivers do not actually
use the data stored there we can simply remove the assignments.

Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
Acked-by: Mauro Carvalho Chehab <mchehab@infradead.org>