vmm: config: Switch VdpaConfig to use PciDeviceCommonConfig

Switch VdpaConfig over to using the newly extracted struct members as
used by all PCI based devices. The use of #[serde(flatten)] means that
this change has no impact on the JSON format that the data is stored as.

Signed-off-by: Rob Bradford <rbradford@meta.com>

vmm/src/vm_config.rs

@@ -647,15 +647,11 @@ impl ApplyLandlock for UserDeviceConfig {
 
 #[derive(Clone, Debug, PartialEq, Eq, Deserialize, Serialize)]
 pub struct VdpaConfig {
+    #[serde(flatten)]
+    pub pci_common: PciDeviceCommonConfig,
     pub path: PathBuf,
     #[serde(default = "default_vdpaconfig_num_queues")]
     pub num_queues: usize,
-    #[serde(default)]
-    pub iommu: bool,
-    #[serde(default)]
-    pub id: Option<String>,
-    #[serde(default)]
-    pub pci_segment: u16,
 }
 
 pub fn default_vdpaconfig_num_queues() -> usize {