avcodec/xfacedec: Add AV_CODEC_CAP_DR1

This decoder uses ff_get_buffer() and does nothing weird
(it does not even rely on any alignment of the frame's data/linesize).

Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

libavcodec/xfacedec.c

@@ -180,6 +180,7 @@ const FFCodec ff_xface_decoder = {
     .p.long_name    = NULL_IF_CONFIG_SMALL("X-face image"),
     .p.type         = AVMEDIA_TYPE_VIDEO,
     .p.id           = AV_CODEC_ID_XFACE,
+    .p.capabilities = AV_CODEC_CAP_DR1,
     .priv_data_size = sizeof(XFaceContext),
     .init           = xface_decode_init,
     FF_CODEC_DECODE_CB(xface_decode_frame),