pcihp: fix possible array out of bounds

Prevent out-of-bounds array access on
acpi_pcihp_pci_status.

Signed-off-by: Gonglei <arei.gonglei@huawei.com>
Reviewed-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Cc: qemu-stable@nongnu.org
Reviewed-by: Marcel Apfelbaum <marcel@redhat.com>
