perf/x86: Fix sparse warnings

FYI, there are new sparse warnings:

 arch/x86/kernel/cpu/perf_event.c:1356:18: sparse: symbol 'events_attr' was not declared. Should it be static?

This patch makes it static and also adds the static keyword to
fix arch/x86/kernel/cpu/perf_event.c:1344:9: warning: symbol
'events_sysfs_show' was not declared.

Signed-off-by: Peter Huewe <peterhuewe@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Cc: fengguang.wu@intel.com
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/n/tip-lerdpXlnruh0yvWs2owwuizl@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>