perf stat: Add AGGR_UNSET mode

Adding AGGR_UNSET mode, so we could distinguish unset aggr_mode in
following patches.

Signed-off-by: Jiri Olsa <[e-mail]>
Tested-by: Kan Liang <[e-mail]>
Cc: David Ahern <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/builtin-stat.c

···
 			csv_sep);
 		break;
 	case AGGR_GLOBAL:
+	case AGGR_UNSET:
 	default:
 		break;
 	}
···
 		case AGGR_GLOBAL:
 		default:
 			fprintf(output, "#           time             counts %*s events\n", unit_width, "unit");
+		case AGGR_UNSET:
+			break;
 		}
 	}
 
···
 		evlist__for_each(evsel_list, counter)
 			print_counter(counter, prefix);
 		break;
+	case AGGR_UNSET:
 	default:
 		break;
 	}
···
 	case AGGR_NONE:
 	case AGGR_GLOBAL:
 	case AGGR_THREAD:
+	case AGGR_UNSET:
 	default:
 		break;
 	}

tools/perf/util/stat.c

···
 			aggr->ena += count->ena;
 			aggr->run += count->run;
 		}
+	case AGGR_UNSET:
 	default:
 		break;
 	}

tools/perf/util/stat.h

···
 	AGGR_SOCKET,
 	AGGR_CORE,
 	AGGR_THREAD,
+	AGGR_UNSET,
 };
 
 struct perf_stat_config {