zephyr: Fix warnings when no alloc

Fix a few warnings that have crept into the code when building without
allocation.

Signed-off-by: David Brown <[email protected]>

Author: d3zd3z

zephyr/src/sys/queue.rs

@@ -6,6 +6,7 @@
 
 use core::ffi::c_void;
 use core::fmt;
+#[cfg(CONFIG_RUST_ALLOC)]
 use core::mem;
 
 use zephyr_sys::{
@@ -15,6 +16,7 @@ use zephyr_sys::{
     k_queue_get,
 };
 
+#[cfg(CONFIG_RUST_ALLOC)]
 use crate::error::Result;
 use crate::sys::K_FOREVER;
 use crate::object::{Fixed, StaticKernelObject, Wrapped};

zephyr/src/sys/sync/mutex.rs

@@ -9,6 +9,7 @@
 //! [`object`]: crate::object
 
 use core::fmt;
+#[cfg(CONFIG_RUST_ALLOC)]
 use core::mem;
 use crate::{
     error::{Result, to_result_void},

zephyr/src/sys/sync/semaphore.rs

@@ -13,6 +13,7 @@
 
 use core::ffi::c_uint;
 use core::fmt;
+#[cfg(CONFIG_RUST_ALLOC)]
 use core::mem;
 
 use crate::{