vo_opengl: call ra_free() in the correct context

This also fixes a double free in vo_opengl_cb.c.

video/out/opengl/video.c

@@ -3499,7 +3499,6 @@ void gl_video_uninit(struct gl_video *p)
     // Should all have been unreffed already.
     assert(!p->num_dr_buffers);
 
-    ra_free(&p->ra);
     talloc_free(p);
 }
 

video/out/vo_opengl.c

@@ -388,6 +388,7 @@ static void uninit(struct vo *vo)
         hwdec_devices_set_loader(vo->hwdec_devs, NULL, NULL);
         hwdec_devices_destroy(vo->hwdec_devs);
     }
+    ra_free(&p->ra);
     mpgl_uninit(p->glctx);
 }