vm-allocator: Align address at allocation time

There is alignment support for AddressAllocator but there are occations
that the alignment is known only when we call allocate(). One example
is PCI BAR which is natually aligned, means for which we have to align
the base address to its size.

Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>

vmm/src/vm.rs

@@ -668,7 +668,7 @@ impl DeviceManager {
                 let size = pmem_cfg.size;
 
                 let pmem_guest_addr = allocator
-                    .allocate_mmio_addresses(None, size as GuestUsize)
+                    .allocate_mmio_addresses(None, size as GuestUsize, None)
                     .ok_or(DeviceManagerError::PmemRangeAllocation)?;
 
                 let (custom_flags, set_len) = if pmem_cfg.file.is_dir() {