avformat/flvdec: use ff_get_extradata()

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

libavformat/flvdec.c

@@ -615,9 +615,8 @@ static int flv_read_close(AVFormatContext *s)
 static int flv_get_extradata(AVFormatContext *s, AVStream *st, int size)
 {
     av_free(st->codec->extradata);
-    if (ff_alloc_extradata(st->codec, size))
+    if (ff_get_extradata(st->codec, s->pb, size) < 0)
         return AVERROR(ENOMEM);
-    avio_read(s->pb, st->codec->extradata, st->codec->extradata_size);
     return 0;
 }