Remove (incorrect) filenames from x264 asm files, add descriptions.

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@17523 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavcodec/x86/h264_deblock_sse2.asm

 ;*****************************************************************************
-;* deblock-a.asm: h264 encoder library
+;* MMX/SSE2-optimized H.264 deblocking code
 ;*****************************************************************************
 ;* Copyright (C) 2005-2008 x264 project
 ;*

libavcodec/x86/h264_idct_sse2.asm

 ;*****************************************************************************
-;* dct-a.asm: h264 encoder library
+;* SSE2-optimized H.264 iDCT
 ;*****************************************************************************
 ;* Copyright (C) 2003-2008 x264 project
 ;*