memcg: mark init_section_page_cgroup() properly

Commit ca371c0d7e23 ("memcg: fix page_cgroup fatal error in FLATMEM")
removes call to alloc_bootmem() in the function so that it can be marked
as __meminit to reduce memory usage when MEMORY_HOTPLUG=n.

Also as the new helper function alloc_page_cgroup() is called only in the
function, it should be marked too.

Signed-off-by: Namhyung Kim <namhyung@gmail.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/page_cgroup.c

@@ -130,7 +130,7 @@ struct page *lookup_cgroup_page(struct page_cgroup *pc)
 	return page;
 }
 
-static void *__init_refok alloc_page_cgroup(size_t size, int nid)
+static void *__meminit alloc_page_cgroup(size_t size, int nid)
 {
 	void *addr = NULL;
 
@@ -162,7 +162,7 @@ static void free_page_cgroup(void *addr)
 }
 #endif
 
-static int __init_refok init_section_page_cgroup(unsigned long pfn)
+static int __meminit init_section_page_cgroup(unsigned long pfn)
 {
 	struct page_cgroup *base, *pc;
 	struct mem_section *section;