V4L/DVB (4610): Add tua6100 config wrapper

I had forgotten to add the wrapper round the tua6100_attach function if its
disabled in Kconfig

Signed-off-by: Andrew de Quincey <adq_dvb@lidskialf.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>