V4L/DVB (5482): Bttv: automatically load dvb-bt8xx for bttv cards with dvb

This patch causes the bttv driver to automatically load the dvb-bt8xx module
for bttv/dvb hybrid cards. Successfully tested with a pcHDTV HD-2000 card.
This patch is based on the recent patches to enable autoloading of cx88-dvb,
cx88-blackbird and saa7134-dvb.

Signed-off-by: Jarod Wilson <jwilson@redhat.com>
Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>