vmm: config: Switch GenericVhostUserConfig to use PciDeviceCommonConfig

Switch GenericVhostUserConfig 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.

As generic vhost-user devices do not support being placed behind an
IOMMU an error is now raised if iommu is set. This can't happen via the
CLI but could via the JSON/API.

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

vmm/src/vm_config.rs

@@ -498,12 +498,10 @@ impl ApplyLandlock for FsConfig {
 
 #[derive(Clone, Debug, PartialEq, Eq, Deserialize, Serialize)]
 pub struct GenericVhostUserConfig {
+    #[serde(flatten)]
+    pub pci_common: PciDeviceCommonConfig,
     pub socket: PathBuf,
     pub queue_sizes: Vec<u16>,
-    #[serde(default)]
-    pub id: Option<String>,
-    #[serde(default)]
-    pub pci_segment: u16,
     pub device_type: u32,
 }