vmm: api: Introduce new "add-device" HTTP endpoint

This commit introduces the new command "add-device" that will let a user
hotplug a VFIO PCI device to an already running VM.

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

vmm/src/device_manager.rs

@@ -1585,6 +1585,10 @@ impl DeviceManager {
         #[cfg(not(feature = "acpi"))]
         return Ok(());
     }
+
+    pub fn add_device(&self, _path: String) -> DeviceManagerResult<()> {
+        Ok(())
+    }
 }
 
 #[cfg(feature = "acpi")]