pci: Remove all Weak references from PciBus

Now that the BusDevice devices are stored as Weak references by the IO
and MMIO buses, there's no need to use Weak references from the PciBus
anymore.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

vmm/src/device_manager.rs

@@ -630,7 +630,7 @@ impl DeviceManager {
             let pci_root = PciRoot::new(None);
             let mut pci_bus = PciBus::new(
                 pci_root,
-                Arc::downgrade(&self.address_manager) as Weak<dyn DeviceRelocation>,
+                Arc::clone(&self.address_manager) as Arc<dyn DeviceRelocation>,
             );
 
             let (iommu_device, iommu_mapping) = if self.config.lock().unwrap().iommu {