rcu: Fix wrong check in list_splice_init_rcu()

If the list to be spliced is empty, then list_splice_init_rcu() has
nothing to do.  Unfortunately, list_splice_init_rcu() does not check
the list to be spliced; it instead checks the list to be spliced into.
This results in memory leaks given current usage.  This commit
therefore fixes the empty-list check.
Signed-off-by: NJan H. Schönherr <schnhrr@cs.tu-berlin.de>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>

include/linux/rculist.h

@@ -183,7 +183,7 @@ static inline void list_splice_init_rcu(struct list_head *list,
 	struct list_head *last = list->prev;
 	struct list_head *at = head->next;
 
-	if (list_empty(head))
+	if (list_empty(list))
 		return;
 
 	/* "first" and "last" tracking list, so initialize it. */