[media] cx88: fix VBI support

Now works with both NTSC and PAL. Tested with CC/XDS for NTSC and
teletext/WSS for PAL. The start lines were wrong, the WSS signal
wasn't captured and there was no difference between NTSC and PAL
w.r.t. the count[] values so NTSC returned way too many lines.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>