[media] bfin_capture: drop unnecessary vb2_is_streaming check

The stop_streaming op is only called if streaming is in progress,
so drop the unnecessary 'if (!vb2_is_streaming(vq))' check.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Pawel Osciak <pawel@osciak.com>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>