V4L/DVB (9923): xc5000: remove init_fw option

The init_fw option was broken for the HVR-950q because we would call the reset
callback inside of dvb_attach() and the callback had not been setup yet.

Michael Krufky (who added the init_fw feature) says it's no longer required,
so just remove the option completely.

Thanks to user Zzeiss from #linuxtv chat for reporting the issue and
Michael Krufky <mkrufky@linuxtv.org> for proposing the fix.

Signed-off-by: Devin Heitmueller <dheitmueller@linuxtv.org>
Acked-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>