northbridge/*/Kconfig: Replace GPLv2 long form headers with SPDX header

Change-Id: Ief2fdedbdba3b7d1708adb2519eb01242e9b52ab
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/41144
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
diff --git a/src/northbridge/amd/agesa/Kconfig b/src/northbridge/amd/agesa/Kconfig
index 1e0153b..42085c4 100644
--- a/src/northbridge/amd/agesa/Kconfig
+++ b/src/northbridge/amd/agesa/Kconfig
@@ -1,16 +1,5 @@
-#
 # 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 published by
-# the Free Software Foundation; version 2 of the License.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
+# SPDX-License-Identifier: GPL-2.0-only
 
 config NORTHBRIDGE_AMD_AGESA
 	bool