treewide: move copyrights and authors to AUTHORS

Also split "this is part of" line from copyright notices.

Change-Id: Ibc2446410bcb3104ead458b40a9ce7819c61a8eb
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/41067
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: David Hendricks <david.hendricks@gmail.com>
Reviewed-by: HAOUAS Elyes <ehaouas@noos.fr>

src/lib/fit.c

@@ -1,9 +1,5 @@
+/* Taken from depthcharge: src/boot/fit.c */
 /*
- * Copyright 2013 Google Inc.
- * Copyright 2018-present Facebook, Inc.
- *
- * Taken from depthcharge: src/boot/fit.c
- *
  * 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; either version 2 of