soc/intel/common/block/smm: add case intrusion to SMI handler

soc/intel/common/block/smm: add case intrusion to SMI handler

This adds case intrusion detection to the SMI handler. At this point one
can add the code to be executed when the INTRUDER signal gets asserted
(iow: when the case is opened).

Examples:
 - issue a warning
 - trigger an NMI
 - call poweroff()
 - ...

Tested on X11SSM-F.

Change-Id: Ifad675bb09215ada760efebdcd915958febf5778
Signed-off-by: Michael Niewöhner <foss@mniewoehner.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/39265
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>