media: v4l2-core: get rid of videobuf-dvb

Videobuf has been replaced by videobuf2. Now, no drivers use
the videobuf-dvb helper module anymore. So, get rid of it.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>