perf events: Update MAINTAINERS entry file patterns

Add file patterns that match relevant files for this subsystem.

Signed-off-by: Vincent Legoll <vincent.legoll@gmail.com>
Cc: Linus Torvalds <torvalds@osdl.org>
Cc: paulus@samba.org
Cc: a.p.zijlstra@chello.nl
LKML-Reference: <4727185d0910130548p325f0185vf4e23b5491c730a0@mail.gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>