perf stat: Fix spelling in comment

Link: http://lkml.kernel.org/r/1315437244-3788-6-git-send-email-jim.cromie@gmail.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>