pci: Reuse pci-bridge hotplug handler handlers for pcie-pci-bridge

These functions are essentially the same, we only have to use
object_get_typename() for reporting errors. So let's share the
implementation of hotplug handler callbacks.

Suggested-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>