V4L/DVB (11438): au0828: fix Kconfig dependance

Fix this build error:
ERROR: "videobuf_queue_vmalloc_init" [drivers/media/video/au0828/au0828.ko] undefined!
ERROR: "videobuf_vmalloc_free" [drivers/media/video/au0828/au0828.ko] undefined!
ERROR: "videobuf_to_vmalloc" [drivers/media/video/au0828/au0828.ko] undefined!

Signed-off-by: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>