perf tools: Ignore 'perf timechart' output file

The default output file produced by the 'perf timechart' tool is called
output.svg, add it to .gitignore.
Signed-off-by: NRamkumar Ramachandra <artagnon@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Link: http://lkml.kernel.org/r/1380789636-4512-1-git-send-email-artagnon@gmail.comSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/.gitignore

@@ -13,6 +13,7 @@ perf*.html
 common-cmds.h
 perf.data
 perf.data.old
+output.svg
 perf-archive
 tags
 TAGS