perf timechart: Fix wrong SVG height

If we call perf timechart with -p 0 arguments, it means we don't want
any tasks related data. It works, but space for tasks data is reserved
in the generated SVG. Remove this unused empty space via passing 0 as
count to the open_svg.
Signed-off-by: Stanislav Fomichev <stfomichev@yandex-team.ru>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1390217980-22424-2-git-send-email-stfomichev@yandex-team.ruSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-timechart.c

@@ -1045,6 +1045,9 @@ static void write_svg_file(struct timechart *tchart, const char *filename)
 		thresh /= 10;
 	} while (!process_filter && thresh && count < tchart->proc_num);
 
+	if (!tchart->proc_num)
+		count = 0;
+
 	open_svg(filename, tchart->numcpus, count, tchart->first_time, tchart->last_time);
 
 	svg_time_grid();