mxfdec: Add missing break in frame layout parsing

Reviewed-by: Tomas Härdin <tomas.hardin@codemill.se>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/mxfdec.c

@@ -1520,6 +1520,7 @@ static int mxf_parse_structural_metadata(MXFContext *mxf)
                 case SeparateFields:
                 case MixedFields:
                     st->codec->height *= 2; /* Turn field height into frame height. */
+                    break;
                 default:
                     av_log(mxf->fc, AV_LOG_INFO, "Unknown frame layout type: %d\n", descriptor->frame_layout);
             }