Flush mp2 as well on seeking. Part of a patch by Brian Brice bbrice gmail com.

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@11506 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavcodec/mpegaudiodec.c

@@ -2642,6 +2642,7 @@ AVCodec mp2_decoder =
     NULL,
     decode_frame,
     CODEC_CAP_PARSE_ONLY,
+    .flush= flush,
 };
 #endif
 #ifdef CONFIG_MP3_DECODER