[media] dabusb: Move it to staging to be deprecated

dabusb driver were conceived as an experimental driver for a test
device. The driver never supported any shipped product, and, while
there were some updates on it in 2003, for an ancient product,
those changes were never submitted upstream.

Also, there's no DocBook for its API, nor any upstream discussion.

So, better to remove it, on .39. If later needed, we may rescue it
from git logs. For now, let's move it to staging.

Acked-by: Deti Fliegl <deti@fliegl.de>
Cc: Deti Fliegl <deti@fliegl.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>