Fix clippy errors

kernel/src/lib.rs

@@ -1,5 +1,15 @@
 #![no_std]
 #![feature(abi_x86_interrupt)]
+#![warn(
+    clippy::correctness,
+    clippy::nursery,
+    clippy::unnecessary_cast,
+    clippy::all,
+    clippy::suspicious,
+    clippy::perf,
+    rustdoc::missing_errors_doc,
+    rustdoc::missing_panics_doc
+)]
 
 extern crate alloc;