cpu/x86: Make SMM stack size configurable

Stoneyridge is running into a stack overflow in the SMM handler.

BUG=b:80539294
TEST=built on grunt

Change-Id: I94e385497bd93c3638c69fb08d9b843c3bbb55ce
Signed-off-by: Raul E Rangel <rrangel@chromium.org>
Reviewed-on: https://review.coreboot.org/27034
Reviewed-by: Martin Roth <martinroth@google.com>
Reviewed-by: Marshall Dawson <marshalldawson3rd@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
2 files changed