V4L/DVB (10216): saa7127: fix broken S-Video with saa7129

Register 0x2d has to be set differently in the saa7129 compared to the
saa7127. This was not done correctly, so S-Video was broken in certain
circumstances.

This fixes a regression introduced in 2.6.28.

Signed-off-by: Martin Dauskardt <martin.dauskardt@gmx.de>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>