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/chardev.rs

@@ -10,11 +10,10 @@
 //! called.
 
 use std::{
-    ffi::CStr,
+    ffi::{c_int, c_void, CStr},
     fmt::{self, Debug},
     io::{self, ErrorKind, Write},
     marker::PhantomPinned,
-    os::raw::{c_int, c_void},
     ptr::addr_of_mut,
     slice,
 };