lavc/vp6: Disable deblock filtering for Simple Profile

In vp6 Advanced Profile, deblock filtering is conditionally enabled in
each frame header.  In Simple Profile it should always be off.  vp6 was
inheriting the wrong default from ff_vp56_init.
Signed-off-by: Ben Jackson <ben@ben.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/vp6.c

@@ -596,6 +596,7 @@ static av_cold int vp6_decode_init(AVCodecContext *avctx)
 
     ff_vp56_init(avctx, avctx->codec->id == AV_CODEC_ID_VP6,
                         avctx->codec->id == AV_CODEC_ID_VP6A);
+    s->deblock_filtering = 0;
     s->vp56_coord_div = vp6_coord_div;
     s->parse_vector_adjustment = vp6_parse_vector_adjustment;
     s->filter = vp6_filter;