hw/i386/acpi-build: Resolve north rather than south bridges

hw/i386/acpi-build: Resolve north rather than south bridges

The code currently assumes Q35 iff ICH9 and i440fx iff PIIX. Now that more
AML generation has been moved into the south bridges and since the
machines define themselves primarily through their north bridges, let's
switch to resolving the north bridges for AML generation instead. This
also allows for easier experimentation with different south bridges in
the "pc" machine, e.g. with PIIX4 and VT82xx.

Signed-off-by: Bernhard Beschow <shentey@gmail.com>
Message-Id: <20221028103419.93398-4-shentey@gmail.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>