rust: sync: lock: Make clippy::undocumented_unsafe_blocks happy

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

Author: hoshinolina

rust/kernel/sync/lock.rs

@@ -211,8 +211,8 @@ impl<T: ?Sized, B: Backend> Guard<'_, T, B> {
         // SAFETY: The caller owns the lock, so it is safe to unlock it.
         unsafe { B::unlock(self.lock.state.get(), &self.state) };
 
-        // SAFETY: The lock was just unlocked above and is being relocked now.
         let _relock =
+            // SAFETY: The lock was just unlocked above and is being relocked now.
             ScopeGuard::new(|| unsafe { B::relock(self.lock.state.get(), &mut self.state) });
 
         cb()