AUTHORS: Move src/arch/arm 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.

Additional changes in this patch:
- Make sure files say that they're part of the coreboot project
- Move descriptions below the license header
- Fix some spacing

Signed-off-by: Martin Roth <martin@coreboot.org>
Change-Id: Id5f26a73f0df366651c076a94975bce1fb321b70
Reviewed-on: https://review.coreboot.org/c/coreboot/+/34605
Reviewed-by: Werner Zeh <werner.zeh@siemens.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/arch/arm/boot.c

@@ -1,8 +1,6 @@
 /*
  * This file is part of the coreboot project.
  *
- * Copyright 2013 Google Inc.
- *
  * 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.