AUTHORS: Move src/cpu/amd copyrights into AUTHORS file

As discussed on the mailing list and voted upon, the coreboot project
is going to move the majority of copyrights out of the headers and into
an AUTHORS file.  This will happen a bit at a time, as we'll be unifying
license headers at the same time.

Signed-off-by: Martin Roth <martin@coreboot.org>
Change-Id: I77275adb7c15b242e319805b8a60b7755fa25db5
Reviewed-on: https://review.coreboot.org/c/coreboot/+/35180
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

src/cpu/amd/pi/00630F01/udelay.c

@@ -1,8 +1,6 @@
 /*
  * This file is part of the coreboot project.
  *
- * Copyright (C) 2014 Alexandru Gagniuc <mr.nuke.me@gmail.com>
- *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; version 2 of the License or (at your option)