PM / wakeirq: report a wakeup_event on dedicated wekup irq

There are two reasons for reporting wakeup event when dedicated wakeup
IRQ is triggered:

- wakeup events accounting, so proper statistical data will be
  displayed in sysfs and debugfs;

- there are small window when System is entering suspend during which
  dedicated wakeup IRQ can be lost:

dpm_suspend_noirq()
  |- device_wakeup_arm_wake_irqs()
      |- dev_pm_arm_wake_irq(X)
         |- IRQ is enabled and marked as wakeup source
[1]...
  |- suspend_device_irqs()
     |- suspend_device_irq(X)
	|- irqd_set(X, IRQD_WAKEUP_ARMED);
	   |- wakup IRQ armed

The wakeup IRQ can be lost if it's triggered at point [1]
and not armed yet.

Hence, fix above cases by adding simple pm_wakeup_event() call in
handle_threaded_wake_irq().

Fixes: 4990d4fe (PM / Wakeirq: Add automated device wake IRQ handling)
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Tested-by: Keerthy <j-keerthy@ti.com>
[ tony@atomide.com: added missing return to avoid warnings ]
Tested-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>