vmm: Create AddressManager to own SystemAllocator

In order to reuse the SystemAllocator later at runtime, it is moved into
the new structure AddressManager. The goal is to have a hold onto the
SystemAllocator and both IO and MMIO buses so that we can use them
later.

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

vmm/src/vm.rs

@@ -701,7 +701,7 @@ impl Vm {
 
         let device_manager = DeviceManager::new(
             &vm_info,
-            &mut allocator,
+            allocator,
             msi_capable,
             userspace_ioapic,
             ram_regions.len() as u32,