[media] firedtv: drop obsolete backend abstraction

Since the drivers/ieee1394/ backend was removed from firedtv, its I/O no
longer needs to be abstracted as exchangeable backend methods.

Also, ieee1394 variants of module and device probe and removal are no
longer there.  Move module probe and removal into firedtv-fw.c where
device probe and removal are implemented.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>