V4L/DVB (3429): Missing break statement on tuner-core

- default_tuner_init was called twice due to a missing break statement.

Signed-off-by: Markus Rechberger <mrechberger@gmail.com>
Acked-by: Michael Krufky <mkrufky@m1k.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>