perf/x86: Implement IBS pmu control ops

Add code to control the IBS pmu. We need to maintain per-cpu
states. Since some states are used and changed by the nmi
handler, access to these states must be atomic.

Signed-off-by: Robert Richter <robert.richter@amd.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1323968199-9326-4-git-send-email-robert.richter@amd.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>