mxfdec: Set AV_FIELD_PROGRESSIVE, needed for AVC-intra

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

libavformat/mxfdec.c

@@ -1524,6 +1524,7 @@ static int mxf_parse_structural_metadata(MXFContext *mxf)
                     av_log(mxf->fc, AV_LOG_INFO, "SegmentedFrame layout isn't currently supported\n");
                     break;
                 case FullFrame:
+                    st->codec->field_order = AV_FIELD_PROGRESSIVE;
                     break;
                 case OneField:
                     /* Every other line is stored and needs to be duplicated. */