ipmi: use a file to load SDRs

ipmi: use a file to load SDRs

The IPMI BMC simulator populates the sdr/sensor tables with a minimal
set of entries (Watchdog). But some qemu platforms might want to use
extra entries for their custom needs.

This patch modifies slighty the initializing routine to take into
account a larger set read from a file. The name of the file to use is
defined through a new 'sdr' property of the simulator device.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
Acked-by: Corey Minyard <cminyard@mvista.com>
Reviewed-by: Marcel Apfelbaum <marcel@redhat.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>