arch/x86: add SMM caller

Useful for debugging or for cases where we need to enter SMM.
Probably should be moved to commonlib or libpayload.

Change-Id: I7a9cc626dae9a7751034615ef409eebc6035f5c3
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-on: https://review.coreboot.org/25193
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
1 file changed