perf/x86: Add 3 new scheduling callbacks

This patch adds 3 new PMU model specific callbacks
during the event scheduling done by x86_schedule_events().

  ->start_scheduling():  invoked when entering the schedule routine.
  ->stop_scheduling():   invoked at the end of the schedule routine
  ->commit_scheduling(): invoked for each committed event

To be used optionally by model-specific code.

Signed-off-by: Maria Dimakopoulou <maria.n.dimakopoulou@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Stephane Eranian <eranian@google.com>
Cc: bp@alien8.de
Cc: jolsa@redhat.com
Cc: kan.liang@intel.com
Link: http://lkml.kernel.org/r/1416251225-17721-4-git-send-email-eranian@google.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>