smbios:ipmi: Ignore IPMI devices with no fwinfo function

Not all devices have fwinfo (like the coming PCI one), so ignore
them if the their fwinfo function is NULL.

Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>

hw/smbios/smbios_type_38.c

@@ -94,6 +94,9 @@ static void smbios_add_ipmi_devices(BusState *bus)
             ii = IPMI_INTERFACE(obj);
             iic = IPMI_INTERFACE_GET_CLASS(obj);
             memset(&info, 0, sizeof(info));
+            if (!iic->get_fwinfo) {
+                continue;
+            }
             iic->get_fwinfo(ii, &info);
             smbios_build_one_type_38(&info);
             continue;