rust: chardev: wrap Chardev with Opaque<>

Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

rust/qemu-api/src/qdev.rs

@@ -334,6 +334,7 @@ where
     fn prop_set_chr(&self, propname: &str, chr: &Owned<Chardev>) {
         assert!(bql_locked());
         let c_propname = CString::new(propname).unwrap();
+        let chr: &Chardev = chr;
         unsafe {
             bindings::qdev_prop_set_chr(
                 self.upcast().as_mut_ptr(),