piix4: disable io on reset

io base register at 0x40 is cleared on reset,
but io is not disabled until some other event
happens to call pm_io_space_update.

Invoke pm_io_space_update directly to make this
consistent.

Cc: qemu-stable@nongnu.org
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/acpi/piix4.c

@@ -380,6 +380,7 @@ static void piix4_reset(void *opaque)
         /* Mark SMM as already inited (until KVM supports SMM). */
         pci_conf[0x5B] = 0x02;
     }
+    pm_io_space_update(s);
     piix4_update_hotplug(s);
 }