openapi: Add missing id property to GenericVhostUserConfig

GenericVhostUserConfig flattens PciDeviceCommonConfig, so the wire
format accepts an optional id like the other PCI device configs.
FsConfig, which flattens the same struct, already documents id.
Add it here as well so generated clients can name the device and
later target it with /vm.remove-device.

Signed-off-by: leo03164 <leo03164@gmail.com>

vmm/src/api/openapi/cloud-hypervisor.yaml

@@ -1263,6 +1263,8 @@ components:
         pci_device_id:
           type: integer
           format: uint8
+        id:
+          type: string
         device_type:
           type: integer
           format: uint32