lavf: use avpriv_find_pix_fmt instead of ff_

Found-by: durandal_1707
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/utils.c

@@ -2962,7 +2962,7 @@ int avformat_find_stream_info(AVFormatContext *ic, AVDictionary **options)
         if (st->codec->codec_type == AVMEDIA_TYPE_VIDEO) {
             if(st->codec->codec_id == AV_CODEC_ID_RAWVIDEO && !st->codec->codec_tag && !st->codec->bits_per_coded_sample){
                 uint32_t tag= avcodec_pix_fmt_to_codec_tag(st->codec->pix_fmt);
-                if(ff_find_pix_fmt(ff_raw_pix_fmt_tags, tag) == st->codec->pix_fmt)
+                if (avpriv_find_pix_fmt(ff_raw_pix_fmt_tags, tag) == st->codec->pix_fmt)
                     st->codec->codec_tag= tag;
             }