[media] dt3155v4l: remove bogus single-frame capture in init_board

For some weird reason an attempt is made in init_board to capture a
single frame. No clue why, and everything works fine without that
code.

I suspect this was test code that was never removed.

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