Instead of scanning IPMI devices from a fwinfo list, allow
the fwinfo to be fetched from the IPMI interface class.
Then the code looking for IPMI fwinfo can scan devices on a
bus and look for ones that implement the IPMI class.

This will let the ACPI scope be defined by the calling
code so the IPMI code doesn't have to know the scope.
Signed-off-by: NCorey Minyard <cminyard@mvista.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>