[media] cx231xx: Fix VBI parameters for sampling rate and offset

The VBI sampling rate and offset were incorrectly specified, which resulted in
CC data not being rendered under zvbi or tvtime.

Set the fields correctly.

Signed-off-by: Devin Heitmueller <dheitmueller@hauppauge.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>