st/vdpau: resolve delayed rendering for GL interop v2

Otherwise OutputSurface interop has funny results sometimes.
This fixes interop with the mpv media player.

v2 (chk): add proper locking

Signed-off-by: Christian König <christian.koenig@amd.com>

src/gallium/state_trackers/vdpau/output.c

@@ -734,5 +734,9 @@ struct pipe_resource *vlVdpOutputSurfaceGallium(VdpOutputSurface surface)
    if (!vlsurface || !vlsurface->surface)
       return NULL;
 
+   pipe_mutex_lock(vlsurface->device->mutex);
+   vlVdpResolveDelayedRendering(vlsurface->device, NULL, NULL);
+   pipe_mutex_unlock(vlsurface->device->mutex);
+
    return vlsurface->surface->texture;
 }