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/platforms/powermac/smp.c

@@ -385,7 +385,6 @@ static void __init psurge_dual_sync_tb(int cpu_nr)
 static struct irqaction psurge_irqaction = {
 	.handler = psurge_primary_intr,
 	.flags = IRQF_DISABLED,
-	.mask = CPU_MASK_NONE,
 	.name = "primary IPI",
 };