mm/page_alloc.c: unexport alloc_pages_exact_nid()

It is only called by mm/page_cgroup.c whcih cannot be modular.
Reported-by: David Rientjes <rientjes@google.com>
Cc: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/page_alloc.c

@@ -2970,7 +2970,6 @@ void * __meminit alloc_pages_exact_nid(int nid, size_t size, gfp_t gfp_mask)
 		return NULL;
 	return make_alloc_exact((unsigned long)page_address(p), order, size);
 }
-EXPORT_SYMBOL(alloc_pages_exact_nid);
 
 /**
  * free_pages_exact - release memory allocated via alloc_pages_exact()