ipmi: Pick up slave address from SMBIOS on an ACPI device

When added by ACPI, the information does not contain the slave address
of the BMC.  However, that information is available from SMBIOS.  So
if we add a device that doesn't have a slave address, look at the other
devices that are duplicate interfaces and see if they have a slave
address.

Signed-off-by: Corey Minyard <cminyard@mvista.com>