rust: use std::ffi instead of std::os::raw

This is allowed since Rust 1.64.0.

Reviewed-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

rust/qemu-api/src/qom.rs

@@ -93,11 +93,10 @@
 //! without incurring into violations of orphan rules for traits.
 
 use std::{
-    ffi::CStr,
+    ffi::{c_void, CStr},
     fmt,
     mem::ManuallyDrop,
     ops::{Deref, DerefMut},
-    os::raw::c_void,
     ptr::NonNull,
 };