media: common: saa7146: disable clipping

The patch removing overlay support also removed the old
saa7146_disable_clipping() function, but that is needed in order
to capture video. Without this the Hexium cards won't show any
video.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Fixes: 7777694f

 ("media: saa7146: drop overlay support")
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>