perf, x86: Pass enable bit mask to __x86_pmu_enable_event()

To reuse this function for events with different enable bit masks,
this mask is part of the function's argument list now.

The function will be used later to control ibs events too.

Signed-off-by: Robert Richter <robert.richter@amd.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1271190201-25705-6-git-send-email-robert.richter@amd.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>