mpeg12dec: Remove incomplete and wrong UV swapping code for VCR2

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 3215140425)

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/mpeg12dec.c

@@ -2038,7 +2038,6 @@ static int vcr2_init_sequence(AVCodecContext *avctx)
     if (s->codec_tag == AV_RL32("BW10")) {
         s->codec_id              = s->avctx->codec_id = AV_CODEC_ID_MPEG1VIDEO;
     } else {
-        exchange_uv(s); // common init reset pblocks, so we swap them here
         s->swap_uv = 1; // in case of xvmc we need to swap uv for each MB
         s->codec_id              = s->avctx->codec_id = AV_CODEC_ID_MPEG2VIDEO;
     }