ipmi: Create a platform device for a DMI-specified IPMI interface

ipmi: Create a platform device for a DMI-specified IPMI interface

Create a platform device for each IPMI device in the DMI table,
a separate kind of device for SSIF types and for KCS, BT, and
SMIC types.  This is so auto-loading IPMI devices will work
from just SMBIOS tables.

This also adds the ability to extract the slave address from
the SMBIOS tables, so that when the driver uses ACPI-specified
interfaces, it can still extract the slave address from SMBIOS.

Signed-off-by: Corey Minyard <cminyard@mvista.com>
Cc: Andy Lutomirski <luto@kernel.org>