hw/pci: Add a busnr property to pci_props and use for acpi/gi

hw/pci: Add a busnr property to pci_props and use for acpi/gi

Using a property allows us to hide the internal details of the PCI device
from the code to build a SRAT Generic Initiator Affinity Structure with
PCI Device Handle.

Suggested-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Message-Id: <20240916171017.1841767-6-Jonathan.Cameron@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>