AUTHORS: Move src/commonlib 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: I4c9351652d81040cc4e7b85bdd1ba85709a74192
Reviewed-on: https://review.coreboot.org/c/coreboot/+/35178
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

src/commonlib/storage/pci_sdhci.c

@@ -1,6 +1,5 @@
 /*
- * Copyright 2013 Google Inc.
- * Copyright 2017 Intel Corporation
+ * This file is part of the coreboot project.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as