Renaming remaining PERF_COUNTERS options into PERF_EVENTS.

Think we can get rid of PERF_COUNTERS now.
Signed-off-by: NRobert Richter <robert.richter@amd.com>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1333643084-26776-5-git-send-email-robert.richter@amd.comSigned-off-by: NIngo Molnar <mingo@kernel.org>