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/libdiracenc.c

@@ -21,7 +21,7 @@
  */
 
 /**
-* @file libavcodec/libdiracenc.c
+* @file
 * Dirac encoding support via libdirac library; more details about the
 * Dirac project can be found at http://dirac.sourceforge.net/.
 * The libdirac_encoder library implements Dirac specification version 2.2