perf, cpu hotplug: Run CPU_STARTING notifiers with irqs disabled

The CPU_STARTING notifiers are supposed to be run with irqs
disabled. But the perf_cpu_notifier() macro invokes them without
doing that. Fix it.

Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: peterz@infradead.org
Cc: acme@ghostprotocols.net
Link: http://lkml.kernel.org/r/20121016075809.3572.47848.stgit@srivatsabhat.in.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>