[media] saa7134: also capture the WSS signal for 50 Hz VBI capture

The saa7134 driver missed capturing line 23 of the VBI area for the
50 Hz formats. Include that line in the VBI capture.

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