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/powerpc/sysdev/cpm1.c

@@ -119,7 +119,6 @@ static irqreturn_t cpm_error_interrupt(int irq, void *dev)
 
 static struct irqaction cpm_error_irqaction = {
 	.handler = cpm_error_interrupt,
-	.mask = CPU_MASK_NONE,
 	.name = "error",
 };