rust: include rust_version in Cargo.toml

Tell clippy the minimum supported Rust version for QEMU.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

rust/hw/char/pl011/Cargo.toml

@@ -9,6 +9,7 @@ resolver = "2"
 publish = false
 keywords = []
 categories = []
+rust-version = "1.63.0"
 
 [lib]
 crate-type = ["staticlib"]

rust/hw/char/pl011/src/device_class.rs

@@ -12,7 +12,6 @@ use qemu_api::{
 
 use crate::device::{PL011Registers, PL011State};
 
-#[allow(clippy::missing_const_for_fn)]
 extern "C" fn pl011_clock_needed(opaque: *mut c_void) -> bool {
     let state = NonNull::new(opaque).unwrap().cast::<PL011State>();
     unsafe { state.as_ref().migrate_clock }