pci, devices, virtio-devices, vmm: Refactor allocate_bars

Refactor PciDevice::allocate_bars trait and all implementations
to take &mut SystemAllocator instead of &Arc<Mutex<SystemAllocator>>,
removing double indirection.

The caller in device_manager.rs now acquires the lock before
calling allocate_bars.

Signed-off-by: Chinmoy <daschinmoyy21@gmail.com>

pci/src/device.rs

@@ -5,7 +5,7 @@
 // SPDX-License-Identifier: Apache-2.0 AND BSD-3-Clause
 
 use std::any::Any;
-use std::sync::{Arc, Barrier, Mutex};
+use std::sync::{Arc, Barrier};
 use std::{io, result};
 
 use serde::{Deserialize, Serialize};
@@ -49,7 +49,7 @@ pub trait PciDevice: Send {
     /// returns an address. Returns a Vec of (GuestAddress, GuestUsize) tuples.
     fn allocate_bars(
         &mut self,
-        _allocator: &Arc<Mutex<SystemAllocator>>,
+        _allocator: &mut SystemAllocator,
         _mmio32_allocator: &mut AddressAllocator,
         _mmio64_allocator: &mut AddressAllocator,
         _resources: Option<Vec<Resource>>,