cpumask: remove references to struct irqaction's mask field.

Impact: cleanup

It's unused, since about 1995.  So remove all initialization of it in
preparation for actually removing the field.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Thomas Gleixner <tglx@linutronix.de>

arch/mips/kernel/i8253.c

@@ -98,7 +98,6 @@ static irqreturn_t timer_interrupt(int irq, void *dev_id)
 static struct irqaction irq0  = {
 	.handler = timer_interrupt,
 	.flags = IRQF_DISABLED | IRQF_NOBALANCING,
-	.mask = CPU_MASK_NONE,
 	.name = "timer"
 };
 
@@ -121,7 +120,6 @@ void __init setup_pit_timer(void)
 	cd->min_delta_ns = clockevent_delta2ns(0xF, cd);
 	clockevents_register_device(cd);
 
-	irq0.mask = cpumask_of_cpu(cpu);
 	setup_irq(0, &irq0);
 }