Since common smbus.c gets built for romstage as well, create a new file
to hold this common code. Account for ICH7 not having a memory BAR, too.
Change-Id: I4ab46750c6fb7f71cbd55848e79ecc3e44cbbd04
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/48364
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>