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/dctref.c

@@ -20,7 +20,7 @@
  */
 
 /**
- * @file libavcodec/dctref.c
+ * @file
  * reference discrete cosine transform (double precision)
  *
  * @author Dylan Yudaken (dyudaken at gmail)