Although there's no reason we COULDN'T use tristate types, we haven't up to this point. If there's a good reason to use them in the future, this check can be removed. Change-Id: I5f1903341f522bc957e394bc0fd288ba1adab431 Signed-off-by: Martin Roth <martinroth@google.com> Reviewed-on: https://review.coreboot.org/13460 Tested-by: build bot (Jenkins) Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>