rust: workqueue: add __rust_helper to helpers

This is needed to inline these helpers into Rust code.

Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://patch.msgid.link/20260105-define-rust-helper-v2-26-51da5f454a67@google.com
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Author: Darksonn

rust/helpers/workqueue.c

@@ -2,9 +2,11 @@
 
 #include <linux/workqueue.h>
 
-void rust_helper_init_work_with_key(struct work_struct *work, work_func_t func,
-				    bool onstack, const char *name,
-				    struct lock_class_key *key)
+__rust_helper void rust_helper_init_work_with_key(struct work_struct *work,
+						  work_func_t func,
+						  bool onstack,
+						  const char *name,
+						  struct lock_class_key *key)
 {
 	__init_work(work, onstack);
 	work->data = (atomic_long_t)WORK_DATA_INIT();