rust: Enable clippy::undocumented_unsafe_blocks lint

Signed-off-by: Asahi Lina <lina@asahilina.net>

Author: hoshinolina

rust/kernel/lib.rs

@@ -28,6 +28,7 @@
 #![feature(const_mut_refs)]
 #![feature(const_ptr_write)]
 #![feature(const_refs_to_cell)]
+#![warn(clippy::undocumented_unsafe_blocks)]
 
 // Ensure conditional compilation based on the kernel configuration works;
 // otherwise we may silently break things like initcall handling.