arch to cpu: Add SPDX license headers to Kconfig files

Change-Id: I7dd7b0b7c5fdb63fe32915b88e69313e3440b64a
Signed-off-by: Martin Roth <gaumless@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/80587
Reviewed-by: Felix Singer <service+coreboot-gerrit@felixsinger.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/console/Kconfig

@@ -1,3 +1,5 @@
+## SPDX-License-Identifier: GPL-2.0-only
+
 menu "Console"
 
 config NO_BOOTBLOCK_CONSOLE