llist: Add llist_next()

So we don't have to expose the struct list_node member.

Cc: Huang Ying <ying.huang@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1315836348.26517.41.camel@twinsSigned-off-by: NIngo Molnar <mingo@elte.hu>

include/linux/llist.h

@@ -138,6 +138,11 @@ static inline bool llist_empty(const struct llist_head *head)
 	return ACCESS_ONCE(head->first) == NULL;
 }
 
+static inline struct llist_node *llist_next(struct llist_node *node)
+{
+	return node->next;
+}
+
 /**
  * llist_add - add a new entry
  * @new:	new entry to be added

kernel/irq_work.c

@@ -110,7 +110,7 @@ void irq_work_run(void)
 	while (llnode != NULL) {
 		work = llist_entry(llnode, struct irq_work, llnode);
 
-		llnode = llnode->next;
+		llnode = llist_next(llnode);
 
 		/*
 		 * Clear the PENDING bit, after this point the @work