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/timer.rs

@@ -3,7 +3,7 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 use std::{
-    os::raw::{c_int, c_void},
+    ffi::{c_int, c_void},
     pin::Pin,
 };