perf stat: Add missing separator in the CSV header

It should have a comma after 'cpus' for socket and die aggregation mode.
The output of the following command shows the issue.

  $ sudo perf stat -a --per-socket -x, --metric-only -I1 true

Before:

                  +--- here
                  V
   time,socket,cpusGhz,insn per cycle,branch-misses of all branches,
       0.000908461,S0,8,0.950,1.65,1.21,

After:

   time,socket,cpus,GHz,insn per cycle,branch-misses of all branches,
       0.000683094,S0,8,0.593,2.00,0.60,
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: James Clark <james.clark@arm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Xing Zhengjun <zhengjun.xing@linux.intel.com>
Link: https://lore.kernel.org/r/20221112032244.1077370-12-namhyung@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/stat-display.c

@@ -828,8 +828,8 @@ static int aggr_header_lens[] = {
 
 static const char *aggr_header_csv[] = {
 	[AGGR_CORE] 	= 	"core,cpus,",
-	[AGGR_DIE] 	= 	"die,cpus",
-	[AGGR_SOCKET] 	= 	"socket,cpus",
+	[AGGR_DIE] 	= 	"die,cpus,",
+	[AGGR_SOCKET] 	= 	"socket,cpus,",
 	[AGGR_NONE] 	= 	"cpu,",
 	[AGGR_THREAD] 	= 	"comm-pid,",
 	[AGGR_NODE] 	= 	"node,",