virtio-devices: move userspace mapping to vm-device

Move UserspaceMapping to vm-device to avoid redefinition since
UserspaceMapping is used by both `virtio-devices` and `device`
crate.

Signed-off-by: Songqian Li <sionli@tencent.com>

virtio-devices/src/device.rs

@@ -15,6 +15,7 @@ use std::thread;
 
 use libc::EFD_NONBLOCK;
 use virtio_queue::Queue;
+use vm_device::UserspaceMapping;
 use vm_memory::{GuestAddress, GuestMemoryAtomic, GuestUsize};
 use vm_migration::{MigratableError, Pausable};
 use vm_virtio::{AccessPlatform, VirtioDeviceType};
@@ -37,15 +38,6 @@ pub trait VirtioInterrupt: Send + Sync {
     }
 }
 
-#[derive(Clone)]
-pub struct UserspaceMapping {
-    pub host_addr: u64,
-    pub mem_slot: u32,
-    pub addr: GuestAddress,
-    pub len: GuestUsize,
-    pub mergeable: bool,
-}
-
 #[derive(Clone)]
 pub struct VirtioSharedMemory {
     pub offset: u64,