mm: don't export __add_pages

This function isn't used by any modules, and is only to be called
from core MM code.  This includes the calls for the add_pages wrapper
that might be inlined.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

mm/memory_hotplug.c

@@ -334,7 +334,6 @@ int __ref __add_pages(int nid, unsigned long phys_start_pfn,
 out:
 	return err;
 }
-EXPORT_SYMBOL_GPL(__add_pages);
 
 #ifdef CONFIG_MEMORY_HOTREMOVE
 /* find the smallest valid pfn in the range [start_pfn, end_pfn) */