zephyr: sys: sync: semaphore: Add missing conditional on alloc

The kio support is behind `CONFIG_RUST_ALLOC`. This needs to be
conditional in addition to the code that uses it.

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

Author: d3zd3z

zephyr/src/sys/sync/semaphore.rs

@@ -25,6 +25,7 @@ use core::task::{Context, Poll};
 #[cfg(CONFIG_RUST_ALLOC)]
 use zephyr_sys::ETIMEDOUT;
 
+#[cfg(CONFIG_RUST_ALLOC)]
 use crate::kio::ContextExt;
 #[cfg(CONFIG_RUST_ALLOC)]
 use crate::time::NoWait;