avrndec: add DR1 capability flag

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

libavcodec/avrndec.c

@@ -126,5 +126,6 @@ AVCodec ff_avrn_decoder = {
     .close          = end,
     .decode         = decode_frame,
     .long_name      = NULL_IF_CONFIG_SMALL("AVRn"),
+    .capabilities   = CODEC_CAP_DR1,
 };