opencv: use the same logic as opencv3 for gstreamer support

The logic for enabling gstreamer support in opencv is not correct. We
select gstreamer-0.10 packages but then we enable gstreamer1 support in
the opencv.mk file. opencv3 has the correct logic, so let's use it in
opencv as well.

Fixes:

  http://autobuild.buildroot.net/results/f6d/f6d0a4ffe347cbb868998856aca674ba8bc2e281/



Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>