perf/x86: Avoid kfree() in CPU_{STARTING,DYING}

On -rt kfree() can schedule, but CPU_{STARTING,DYING} should be
atomic. So use a list to defer kfree until CPU_{ONLINE,DEAD}.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: peterz@infradead.org
Cc: eranian@google.com
Cc: ak@linux.intel.com
Link: http://lkml.kernel.org/r/1366113067-3262-2-git-send-email-zheng.z.yan@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>