avformat/img2dec: remove functions from image pipe which are unneeded for image pipes

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

libavformat/img2dec.c

@@ -670,8 +670,6 @@ AVInputFormat ff_image_ ## imgname ## _pipe_demuxer = {\
     .read_probe     = imgname ## _probe,\
     .read_header    = ff_img_read_header,\
     .read_packet    = ff_img_read_packet,\
-    .read_close     = img_read_close,\
-    .read_seek      = img_read_seek,\
     .priv_class     = & imgname ## _class,\
     .raw_codec_id   = codecid,\
 };