rust: blk: add __rust_helper to helpers

This is needed to inline these helpers into Rust code.

Reviewed-by: Boqun Feng <[email protected]>
Reviewed-by: Gary Guo <[email protected]>
Signed-off-by: Alice Ryhl <[email protected]>

Author: Darksonn

rust/helpers/blk.c

@@ -3,12 +3,12 @@
 #include <linux/blk-mq.h>
 #include <linux/blkdev.h>
 
-void *rust_helper_blk_mq_rq_to_pdu(struct request *rq)
+__rust_helper void *rust_helper_blk_mq_rq_to_pdu(struct request *rq)
 {
 	return blk_mq_rq_to_pdu(rq);
 }
 
-struct request *rust_helper_blk_mq_rq_from_pdu(void *pdu)
+__rust_helper struct request *rust_helper_blk_mq_rq_from_pdu(void *pdu)
 {
 	return blk_mq_rq_from_pdu(pdu);
 }