vo_rpi: partially undeprecate

Using vo_opengl + MMAL overlay didn't quite work out.

video/out/vo.c

@@ -63,6 +63,9 @@ extern const struct vo_driver video_out_tct;
 
 const struct vo_driver *const video_out_drivers[] =
 {
+#if HAVE_RPI
+    &video_out_rpi,
+#endif
 #if HAVE_GL
     &video_out_opengl,
 #endif
@@ -102,9 +105,6 @@ const struct vo_driver *const video_out_drivers[] =
 #endif
 #if HAVE_GL
     &video_out_opengl_cb,
-#endif
-#if HAVE_RPI
-    &video_out_rpi,
 #endif
     NULL
 };

video/out/vo_rpi.c

@@ -869,9 +869,6 @@ static void uninit(struct vo *vo)
 
 static int preinit(struct vo *vo)
 {
-    MP_WARN(vo, "This VO is deprecated! Use --vo=opengl instead (which has "
-                "the same features and which is the default).\n");
-
     struct priv *p = vo->priv;
 
     p->background_layer = p->layer;