/proc/pagetypeinfo: fix output for memoryless nodes

on memoryless node, /proc/pagetypeinfo is displayed slightly funny output.
this patch fix it.

output example (header is outputed, but no data is outputed)
--------------------------------------------------------------
Page block order: 14
Pages per block:  16384

Free pages count per migrate type at order       0      1      2      3      4      5    \
  6      7      8      9     10     11     12     13     14     15     16

Number of blocks type     Unmovable  Reclaimable      Movable      Reserve      Isolate
Page block order: 14
Pages per block:  16384

Free pages count per migrate type at order       0      1      2      3      4      5    \
  6      7      8      9     10     11     12     13     14     15     16
Signed-off-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: NMel Gorman <mel@csn.ul.ie>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/vmstat.c

@@ -548,6 +548,10 @@ static int pagetypeinfo_show(struct seq_file *m, void *arg)
 {
 	pg_data_t *pgdat = (pg_data_t *)arg;
 
+	/* check memoryless node */
+	if (!node_state(pgdat->node_id, N_HIGH_MEMORY))
+		return 0;
+
 	seq_printf(m, "Page block order: %d\n", pageblock_order);
 	seq_printf(m, "Pages per block:  %lu\n", pageblock_nr_pages);
 	seq_putc(m, '\n');