hw/i386/acpi_build.c: Avoid shifting left into sign bit

Add U suffix to avoid undefined behaviour.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

hw/i386/acpi-build.c

@@ -907,7 +907,7 @@ static void build_pci_bus_end(PCIBus *bus, void *bus_state)
 
             build_append_byte(notify, 0x7B); /* AndOp */
             build_append_byte(notify, 0x68); /* Arg0Op */
-            build_append_int(notify, 0x1 << i);
+            build_append_int(notify, 0x1U << i);
             build_append_byte(notify, 0x00); /* NullName */
             build_append_byte(notify, 0x86); /* NotifyOp */
             build_append_nameseg(notify, "S%.02X_", PCI_DEVFN(i, 0));