vpx: keep the multiview_mode from the demux

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/codec/vpx.c

@@ -247,6 +247,7 @@ static int Decode(decoder_t *dec, block_t *block)
     }
 
     dec->fmt_out.video.projection_mode = dec->fmt_in.video.projection_mode;
+    dec->fmt_out.video.multiview_mode = dec->fmt_in.video.multiview_mode;
     dec->fmt_out.video.pose = dec->fmt_in.video.pose;
 
     if (decoder_UpdateVideoFormat(dec))