This patch against 2.5 gets rid of the following annoying but
harmless messages when booting a generic kernel on a non-ZX1 box:

        No IOC for PCI Bus 0000:00 in ACPI
        No IOC for PCI Bus 0000:01 in ACPI
        ...

We just forgot to bail out of the SBA IOMMU init function if it didn't
find any SBA hardware.