perf script: use ARRAY_SIZE instead of reinventing it

Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1356030701-16284-11-git-send-email-sasha.levin@oracle.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>