proresdsp: Correct credits to point to the Author and not just the code this is based on.

Also change Libav to FFmpeg
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/x86/proresdsp.asm

 ;******************************************************************************
 ;* x86-SIMD-optimized IDCT for prores
-;* this is identical to "simple" IDCT except for the clip range
+;* this is identical to "simple" IDCT written by Michael Niedermayer
+;* except for the clip range
 ;*
 ;* Copyright (c) 2011 Ronald S. Bultje <rsbultje@gmail.com>
 ;*
-;* This file is part of Libav.
+;* This file is part of FFmpeg.
 ;*
-;* Libav is free software; you can redistribute it and/or
+;* FFmpeg is free software; you can redistribute it and/or
 ;* modify it under the terms of the GNU Lesser General Public
 ;* License as published by the Free Software Foundation; either
 ;* version 2.1 of the License, or (at your option) any later version.
 ;*
-;* Libav is distributed in the hope that it will be useful,
+;* FFmpeg is distributed in the hope that it will be useful,
 ;* but WITHOUT ANY WARRANTY; without even the implied warranty of
 ;* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 ;* Lesser General Public License for more details.
 ;*
 ;* You should have received a copy of the GNU Lesser General Public
-;* License along with Libav; if not, write to the Free Software
+;* License along with FFmpeg; if not, write to the Free Software
 ;* 51, Inc., Foundation Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 ;******************************************************************************