vo_opengl: improve queue size heuristic

The default scaling was a slight bit too low, which could cause buffer
underruns in some cases.

This should improve the result when using tscale filters other than
oversample. The oversample case should be unaffected.

video/out/gl_video.c

@@ -2442,7 +2442,7 @@ void gl_video_set_options(struct gl_video *p, struct gl_video_opts *opts,
         if (kernel) {
             double radius = kernel->radius;
             radius = radius > 0 ? radius : p->opts.scaler_radius[2];
-           *queue_size = 50e3 * (ceil(radius) - 1);
+           *queue_size = 50e3 * ceil(radius);
         }
     }