D3D vout: don't spam too much the messages in release mode

modules/video_output/msw/direct3d.c

@@ -1221,8 +1221,10 @@ static void Direct3DImportSubpicture(vout_display_t *vd,
                 cache->format == sys->d3dregion_format &&
                 cache->width  == r->fmt.i_visible_width &&
                 cache->height == r->fmt.i_visible_height) {
+#ifndef NDEBUG
                 msg_Dbg(vd, "Reusing %dx%d texture for OSD",
                         cache->width, cache->height);
+#endif
                 *d3dr = *cache;
                 memset(cache, 0, sizeof(*cache));
             }