mm: fix section mismatch in memory_hotplug.c

__free_pages_bootmem() is a __meminit function - which has been called
from put_pages_bootmem thus causes a section mismatch warning.

 We were warned by the following warning:

  LD      mm/built-in.o
WARNING: mm/built-in.o(.text+0x26b22): Section mismatch in reference
from the function put_page_bootmem() to the function
.meminit.text:__free_pages_bootmem()
The function put_page_bootmem() references
the function __meminit __free_pages_bootmem().
This is often because put_page_bootmem lacks a __meminit
annotation or the annotation of __free_pages_bootmem is wrong.
Signed-off-by: Rakib Mullick <rakib.mullick@gmail.com>
Cc: Yasunori Goto <y-goto@jp.fujitsu.com>
Cc: Badari Pulavarty <pbadari@us.ibm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memory_hotplug.c

@@ -72,7 +72,9 @@ static void get_page_bootmem(unsigned long info,  struct page *page, int type)
 	atomic_inc(&page->_count);
 }
 
-void put_page_bootmem(struct page *page)
+/* reference to __meminit __free_pages_bootmem is valid
+ * so use __ref to tell modpost not to generate a warning */
+void __ref put_page_bootmem(struct page *page)
 {
 	int type;