pc:piix4: Update smbus I/O space after a migration

Otherwise it won't be set up correctly and won't work after
miigration.

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

hw/acpi/piix4.c

@@ -173,6 +173,7 @@ static int vmstate_acpi_post_load(void *opaque, int version_id)
     PIIX4PMState *s = opaque;
 
     pm_io_space_update(s);
+    smbus_io_space_update(s);
     return 0;
 }