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/frv/kernel/time.c

@@ -45,7 +45,6 @@ static irqreturn_t timer_interrupt(int irq, void *dummy);
 static struct irqaction timer_irq  = {
 	.handler = timer_interrupt,
 	.flags = IRQF_DISABLED,
-	.mask = CPU_MASK_NONE,
 	.name = "timer",
 };