irq: Remove unnecessary warning with affinity_hint

Hi,

If you turn off a PCI device whose driver has set affinity_hint, you will get warning message which does _not_ explain the reason why it is appeared from the users' point of view.

  # echo 0 > /sys/bus/pci/slots/65/power

  Apr 28 20:29:39 localhost kernel: ------------[ cut here ]------------
  Apr 28 20:29:39 localhost kernel: WARNING: at kernel/irq/manage.c:1002 __free_irq+0x22d/0x250() (Tainted: P           ---------------   )
  (snip)

Users will misunderstand some problem has happened even though he or she succeeded to turn off the device. I suppose this warning was originally for a debug purpose for driver developers and has incidentally been left.

Just remove the warning is good and enough.

@@ -1335,7 +1335,7 @@ static struct irqaction *__free_irq(unsi
 
 #ifdef CONFIG_SMP
 	/* make sure affinity_hint is cleaned up */
-	if (WARN_ON_ONCE(desc->affinity_hint))
+	if (desc->affinity_hint)
 		desc->affinity_hint = NULL;
 #endif