vmm: Device name verification based on DeviceTree

Instead of relying on a PCI specific device list, we use the DeviceTree
as a reference to determine if a device name is already in use or not.

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

vmm/src/device_tree.rs

@@ -51,6 +51,9 @@ impl DeviceTree {
     pub fn new() -> Self {
         DeviceTree(HashMap::new())
     }
+    pub fn contains_key(&self, k: &str) -> bool {
+        self.0.contains_key(k)
+    }
     pub fn get(&self, k: &str) -> Option<&DeviceNode> {
         self.0.get(k)
     }