vmm: add NVIDIA GPUDirect P2P support

On platforms where PCIe P2P is supported, inject a PCI capability into
NVIDIA GPU to indicate support.

Signed-off-by: Thomas Barrett <tbarrett@crusoeenergy.com>

vmm/src/device_manager.rs

@@ -3510,6 +3510,7 @@ impl DeviceManager {
             pci_device_bdf,
             Arc::new(move || memory_manager.lock().unwrap().allocate_memory_slot()),
             vm_migration::snapshot_from_id(self.snapshot.as_ref(), vfio_name.as_str()),
+            device_cfg.x_nv_gpudirect_clique,
         )
         .map_err(DeviceManagerError::VfioPciCreate)?;