dvbdevice: Don't pass BPF parameter yet

The SCR/Unicable configuration is complete yet. So, it makes
no sense to pass a bogus BPF value to the DVB backend.

Also, at least here, config->bpf was initialized with a bogus
value, causing tune to fail.

While here, remove a legacy code that was previously commented out.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>