perf/core: Correct files in MAINTAINERS entry

This corrects the file entries for perf_events. The following
files are caught now:

 $ xargs | eval ls $(cat) | sort -u
 kernel/perf_event*.c
 include/linux/perf_event.h
 arch/*/kernel/perf_event*.c
 arch/*/kernel/*/perf_event*.c
 arch/*/kernel/*/*/perf_event*.c
 arch/*/include/asm/perf_event.h
 arch/*/lib/perf_event*.c
 arch/*/kernel/perf_callchain.c

 arch/alpha/include/asm/perf_event.h
 arch/arm/include/asm/perf_event.h
 arch/arm/kernel/perf_event.c
 arch/frv/include/asm/perf_event.h
 arch/frv/lib/perf_event.c
 arch/parisc/include/asm/perf_event.h
 arch/powerpc/include/asm/perf_event.h
 arch/powerpc/kernel/perf_callchain.c
 arch/powerpc/kernel/perf_event.c
 arch/s390/include/asm/perf_event.h
 arch/sh/include/asm/perf_event.h
 arch/sh/kernel/cpu/sh4a/perf_event.c
 arch/sh/kernel/cpu/sh4/perf_event.c
 arch/sh/kernel/perf_callchain.c
 arch/sh/kernel/perf_event.c
 arch/sparc/include/asm/perf_event.h
 arch/sparc/kernel/perf_event.c
 arch/x86/include/asm/perf_event.h
 arch/x86/kernel/cpu/perf_event_amd.c
 arch/x86/kernel/cpu/perf_event.c
 arch/x86/kernel/cpu/perf_event_intel.c
 arch/x86/kernel/cpu/perf_event_p6.c
 include/linux/perf_event.h
 kernel/perf_event.c

Signed-off-by: Robert Richter <robert.richter@amd.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1268826553-19518-3-git-send-email-robert.richter@amd.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>