perf/core, x86: Remove duplicate perf_event_mask variable

The same information is stored also in x86_pmu.intel_ctrl. This
patch removes perf_event_mask and instead uses
x86_pmu.intel_ctrl directly.

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: <1268826553-19518-5-git-send-email-robert.richter@amd.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>