mm/memory_hotplug : fix section mismatch

With CONFIG_MEMORY_HOTPLUG I got following warning:

WARNING: vmlinux.o(.text+0x1276b0): Section mismatch in reference from the function hotadd_new_pgdat() to the function .meminit.text:free_area_init_node()
The function hotadd_new_pgdat() references
the function __meminit free_area_init_node().
This is often because hotadd_new_pgdat lacks a __meminit annotation or the annotation of free_area_init_node is wrong.

Use __ref to fix this.

---
 mm/memory_hotplug.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

index 821dee5..380aef4 100644
@@ -447,7 +447,8 @@ int online_pages(unsigned long pfn, unsigned long nr_pages)
 }
 #endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */
 
-static pg_data_t *hotadd_new_pgdat(int nid, u64 start)
+/* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */
+static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start)
 {
 	struct pglist_data *pgdat;
 	unsigned long zones_size[MAX_NR_ZONES] = {0};

1.6.5.2