Remove explicit filename from Doxygen @file commands.

Passing an explicit filename to this command is only necessary if the
documentation in the @file block refers to a file different from the
one the block resides in.

Originally committed as revision 22921 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/wavpack.c

@@ -24,7 +24,7 @@
 #include "unary.h"
 
 /**
- * @file libavcodec/wavpack.c
+ * @file
  * WavPack lossless audio decoder
  */