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/jazz/irq.c

@@ -134,7 +134,6 @@ static irqreturn_t r4030_timer_interrupt(int irq, void *dev_id)
 static struct irqaction r4030_timer_irqaction = {
 	.handler	= r4030_timer_interrupt,
 	.flags		= IRQF_DISABLED,
-	.mask		= CPU_MASK_CPU0,
 	.name		= "R4030 timer",
 };