chroma_qscale seems not used anywhere for mpeg1/2 so dont waste cpu time setting it

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@9842 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavcodec/mpeg12.c

@@ -1739,7 +1739,6 @@ static int mpeg_decode_slice(Mpeg1Context *s1, int mb_y,
 #endif
 
         ret = mpeg_decode_mb(s, s->block);
-        s->chroma_qscale= s->qscale;
 
         dprintf(s->avctx, "ret=%d\n", ret);
         if (ret < 0)