d3d11_tonemap: log when the TrueHDR feature is not available

That is the case for win32 builds on win64.

modules/video_output/win32/d3d11_tonemap.cpp

@@ -117,6 +117,7 @@ d3d11_tonemapper *D3D11_TonemapperCreate(vlc_object_t *vd, d3d11_device_t *d3d_d
 
         if (!available)
         {
+            msg_Warn(vd, "True HDR not supported");
             d3d11_device_unlock(d3d_dev);
             goto error;
         }