acpi: ich9: allow guest to clear SCI rised by GPE

it fixes IRQ storm since guest isn't able to lower SCI IRQ
after it has been handled when it clears GPE event.
Signed-off-by: NIgor Mammedov <imammedo@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

hw/acpi/ich9.c

@@ -61,6 +61,7 @@ static void ich9_gpe_writeb(void *opaque, hwaddr addr, uint64_t val,
 {
     ICH9LPCPMRegs *pm = opaque;
     acpi_gpe_ioport_writeb(&pm->acpi_regs, addr, val);
+    acpi_update_sci(&pm->acpi_regs, pm->irq);
 }
 
 static const MemoryRegionOps ich9_gpe_ops = {