saa7134-dvb: add missing dvb_attach around tda10046_attach

This patch adds a possibly missing dvb_attach for tda10046_attach.
This removes the hard dependency of saa7134-dvb on tda1004x module.
Signed-off-by: Matthias Schwarzott <zzam@gentoo.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>