virtio-devices: mem, balloon: Use struct initialisation

error: field assignment outside of initializer for an instance created with Default::default()
   --> virtio-devices/src/mem.rs:496:9
    |
496 |         resp.resp_type = resp_type;
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
note: consider initializing the variable with `mem::VirtioMemResp { resp_type: resp_type, ..Default::default() }` and removing relevant reassignments
   --> virtio-devices/src/mem.rs:495:9
    |
495 |         let mut resp = VirtioMemResp::default();
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#field_reassign_with_default

Signed-off-by: Rob Bradford <robert.bradford@intel.com>

virtio-devices/src/balloon.rs

@@ -321,8 +321,10 @@ impl Balloon {
     pub fn new(id: String, size: u64, seccomp_action: SeccompAction) -> io::Result<Self> {
         let avail_features = 1u64 << VIRTIO_F_VERSION_1;
 
-        let mut config = VirtioBalloonConfig::default();
-        config.num_pages = (size >> VIRTIO_BALLOON_PFN_SHIFT) as u32;
+        let config = VirtioBalloonConfig {
+            num_pages: (size >> VIRTIO_BALLOON_PFN_SHIFT) as u32,
+            ..Default::default()
+        };
 
         Ok(Balloon {
             common: VirtioCommon {

virtio-devices/src/mem.rs

@@ -489,12 +489,14 @@ impl MemEpollHandler {
     fn virtio_mem_send_response(
         mem: &GuestMemoryMmap,
         resp_type: u16,
-        resp_state: u16,
+        state: u16,
         status_addr: GuestAddress,
     ) -> u32 {
-        let mut resp = VirtioMemResp::default();
-        resp.resp_type = resp_type;
-        resp.state.state = resp_state;
+        let resp = VirtioMemResp {
+            resp_type,
+            state: VirtioMemRespState { state },
+            ..Default::default()
+        };
         match mem.write_obj(resp, status_addr) {
             Ok(_) => size_of::<VirtioMemResp>() as u32,
             Err(e) => {