mm/sparse: use page_private() to get page->private value

free_map_bootmem() uses page->private directly to set
removing_section_nr argument.  But to get page->private value,
page_private() has been prepared.

So free_map_bootmem() should use page_private() instead of
page->private.

Link: http://lkml.kernel.org/r/1d34eaa5-a506-8b7a-6471-490c345deef8@gmail.com
Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Xishi Qiu <qiuxishi@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/sparse.c

@@ -667,7 +667,7 @@ static void free_map_bootmem(struct page *memmap)
 		BUG_ON(magic == NODE_INFO);
 
 		maps_section_nr = pfn_to_section_nr(page_to_pfn(page));
-		removing_section_nr = page->private;
+		removing_section_nr = page_private(page);
 
 		/*
 		 * When this function is called, the removing section is