MAINTAINERS: Add Arnaldo as tools/perf/ co-maintainer

Acked-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: NPaul Mackerras <paulus@samba.org>
Acked-by: NArnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <new-submission>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

MAINTAINERS

@@ -4221,6 +4221,7 @@ PERFORMANCE EVENTS SUBSYSTEM
 M:	Peter Zijlstra <a.p.zijlstra@chello.nl>
 M:	Paul Mackerras <paulus@samba.org>
 M:	Ingo Molnar <mingo@elte.hu>
+M:	Arnaldo Carvalho de Melo <acme@redhat.com>
 S:	Supported
 F:	kernel/perf_event.c
 F:	include/linux/perf_event.h