V4L/DVB (4428): Fix tda826x detection

The tda826x detection was (correctly) cleaned up earlier, but unfortunately
changing the number of received i2c messages from 2 -> 1 was missed. This
fixes it.

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