perf stat: Fix crash with --per-node --metric-only in CSV mode

The following command will get segfault due to missing aggr_header_csv
for AGGR_NODE:

$ sudo perf stat -a --per-node -x, --metric-only true

Committer testing:

Before this patch:

# perf stat -a --per-node -x, --metric-only true
Segmentation fault (core dumped)
#

After:

# gdb perf
-bash: gdb: command not found
# perf stat -a --per-node -x, --metric-only true
node,Ghz,frontend cycles idle,backend cycles idle,insn per cycle,branch-misses of all branches,
N0,32,0.335,2.10,0.65,0.69,0.03,1.92,
#

Fixes: 86895b480a2f10c7 ("perf stat: Add --per-node agregation support")
Signed-off-by: Namhyung Kim <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Ian Rogers <[e-mail]>
Cc: James Clark <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Kan Liang <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Xing Zhengjun <[e-mail]>
Link: http://lore.kernel.org/lkml/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/stat-display.c

···
 			[AGGR_CORE] = 2,
 			[AGGR_THREAD] = 1,
 			[AGGR_UNSET] = 0,
-			[AGGR_NODE] = 0,
+			[AGGR_NODE] = 1,
 		};
 
 		pm = config->metric_only ? print_metric_only_csv : print_metric_csv;
···
 	[AGGR_SOCKET] = 12,
 	[AGGR_NONE] = 6,
 	[AGGR_THREAD] = 24,
+	[AGGR_NODE] = 6,
 	[AGGR_GLOBAL] = 0,
 };
 
···
 	[AGGR_SOCKET] 	= 	"socket,cpus",
 	[AGGR_NONE] 	= 	"cpu,",
 	[AGGR_THREAD] 	= 	"comm-pid,",
+	[AGGR_NODE] 	= 	"node,",
 	[AGGR_GLOBAL] 	=	""
 };