list: Don't use WRITE_ONCE() in hlist_add_behind()

Commit 1c97be6 ("list: Use WRITE_ONCE() when adding to lists and
hlists") introduced the use of WRITE_ONCE() to atomically write the list
head's ->next pointer.

hlist_add_behind() doesn't touch the hlist head's ->first pointer so
there is no reason to use WRITE_ONCE() in this case.

Co-developed-by: Ilias Tsitsimpis <[email protected]>
Signed-off-by: Nikos Tsironis <[email protected]>
Reviewed-by: Paul E. McKenney <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>

include/linux/list.h

@@ -754,7 +754,7 @@ static inline void hlist_add_behind(struct hlist_node *n,
 				    struct hlist_node *prev)
 {
 	n->next = prev->next;
-	WRITE_ONCE(prev->next, n);
+	prev->next = n;
 	n->pprev = &prev->next;
 
 	if (n->next)