mm/page_alloc.c: use '__paginginit' instead of '__init'

set_pageblock_order() may be called when memory hotplug, so need use
'__paginginit' instead of '__init'.

The related warning:

  The function __meminit .free_area_init_node() references
  a function __init .set_pageblock_order().
  If .set_pageblock_order is only used by .free_area_init_node then
  annotate .set_pageblock_order with a matching annotation.
Signed-off-by: NChen Gang <gang.chen@asianux.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/page_alloc.c

@@ -4586,7 +4586,7 @@ static inline void setup_usemap(struct pglist_data *pgdat, struct zone *zone,
 #ifdef CONFIG_HUGETLB_PAGE_SIZE_VARIABLE
 
 /* Initialise the number of pages represented by NR_PAGEBLOCK_BITS */
-void __init set_pageblock_order(void)
+void __paginginit set_pageblock_order(void)
 {
 	unsigned int order;
 
@@ -4614,7 +4614,7 @@ void __init set_pageblock_order(void)
  * include/linux/pageblock-flags.h for the values of pageblock_order based on
  * the kernel config
  */
-void __init set_pageblock_order(void)
+void __paginginit set_pageblock_order(void)
 {
 }