irq.h: remove padding from irq_desc on 64bits

Impact: reduce struct irq_desc size

struct irq_desc: reorder to remove padding on 64bits

shrinks irq_desc to 128 bytes which saves data space & cache lines

On a generic x86_64/SMP build this reduces the reported data size by
64k.

Signed-off-by: Richard Kennedy <richard@rsk.demon.co.uk>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/linux/irq.h

@@ -142,8 +142,8 @@ struct irq_chip {
  * @depth:		disable-depth, for nested irq_disable() calls
  * @wake_depth:		enable depth, for multiple set_irq_wake() callers
  * @irq_count:		stats field to detect stalled irqs
- * @irqs_unhandled:	stats field for spurious unhandled interrupts
  * @last_unhandled:	aging timer for unhandled count
+ * @irqs_unhandled:	stats field for spurious unhandled interrupts
  * @lock:		locking for SMP
  * @affinity:		IRQ affinity on SMP
  * @cpu:		cpu index useful for balancing
@@ -165,8 +165,8 @@ struct irq_desc {
 	unsigned int		depth;		/* nested irq disables */
 	unsigned int		wake_depth;	/* nested wake enables */
 	unsigned int		irq_count;	/* For detecting broken IRQs */
-	unsigned int		irqs_unhandled;
 	unsigned long		last_unhandled;	/* Aging timer for unhandled count */
+	unsigned int		irqs_unhandled;
 	spinlock_t		lock;
 #ifdef CONFIG_SMP
 	cpumask_t		affinity;