perf: Ignore perf.data.old

Tell git to ignore this file.
Signed-off-by: NWANG Cong <amwang@redhat.com>
LKML-Reference: <20100125051052.3999.28082.sendpatchset@localhost.localdomain>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

tools/perf/.gitignore

@@ -13,6 +13,7 @@ perf*.xml
 perf*.html
 common-cmds.h
 perf.data
+perf.data.old
 tags
 TAGS
 cscope*