Basically whenever the VO does a redraw, we always have to flip buffers
for vo_drm and drm_egl. The old way of doing this was checking if the
video was paused and if the frame was still. This does work, but what
really needs to be known is simply if the VO is redrawing. Since the
added VOCTRL_REDRAW tells us this, we can shuffle around some logic and
simplify greatly. drm_egl no longer needs its custom override for the
submit_frame step so that can be eliminated along with the vo_gpu_next
hack.
Fixes 0959cdeb03.
Dudemanguy
1bcc76d7f1