coreinfo: Use SPDX license identifiers

- Remove copyright notices and add authors to AUTHORS
- Use SPDX license identifiers for all files
- Add coreinfo to the license header lint

Signed-off-by: Jacob Garber <jgarber1@ualberta.ca>
Change-Id: Ib0c5328a4027849b1eda4f57141a898335230726
Reviewed-on: https://review.coreboot.org/c/coreboot/+/45178
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: HAOUAS Elyes <ehaouas@noos.fr>
Reviewed-by: Martin Roth <martinroth@google.com>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

payloads/coreinfo/Kconfig

@@ -1,7 +1,3 @@
-##
-##
-## Copyright (C) 2008 Uwe Hermann <uwe@hermann-uwe.de>
-##
 ## SPDX-License-Identifier: GPL-2.0-only
 
 # For a description of the syntax of this configuration file,