Make mp4_read_descr static: It is only used inside libavformat/mov.c.

Originally committed as revision 22097 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/mov.c

@@ -396,7 +396,7 @@ int ff_mp4_read_descr_len(ByteIOContext *pb)
     return len;
 }
 
-int mp4_read_descr(AVFormatContext *fc, ByteIOContext *pb, int *tag)
+static int mp4_read_descr(AVFormatContext *fc, ByteIOContext *pb, int *tag)
 {
     int len;
     *tag = get_byte(pb);