ACPI processor: Fix tick_broadcast_mask online/offline regression

In commit 99b725084 "ACPI processor hotplug: Delay acpi_processor_start()
call for hotplugged cores", acpi_processor_hotplug(pr) was wrongly replaced
by acpi_processor_cst_has_changed() inside the acpi_cpu_soft_notify(). This
patch will restore it back, fixing the tick_broadcast_mask regression:
	https://lkml.org/lkml/2012/7/30/169

Signed-off-by: Feng Tang <feng.tang@intel.com>
Cc: Thomas Renninger <trenn@suse.de>
Cc: <stable@vger.kernel.org> # 3.3+
Reviewed-by: Rafael J. Wysocki <rjw@sisk.pl>
Reviewed-by: Deepthi Dharwar <deepthi@linux.vnet.ibm.com>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/acpi/processor_driver.c

@@ -442,7 +442,7 @@ static int acpi_cpu_soft_notify(struct notifier_block *nfb,
 		/* Normal CPU soft online event */
 		} else {
 			acpi_processor_ppc_has_changed(pr, 0);
-			acpi_processor_cst_has_changed(pr);
+			acpi_processor_hotplug(pr);
 			acpi_processor_reevaluate_tstate(pr, action);
 			acpi_processor_tstate_has_changed(pr);
 		}