cpumask: convert struct clock_event_device to cpumask pointers.

Impact: change calling convention of existing clock_event APIs

struct clock_event_timer's cpumask field gets changed to take pointer,
as does the ->broadcast function.

Another single-patch change.  For safety, we BUG_ON() in
clockevents_register_device() if it's not set.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Ingo Molnar <mingo@elte.hu>

arch/arm/mach-at91/at91rm9200_time.c

@@ -169,7 +169,6 @@ static struct clock_event_device clkevt = {
 	.features	= CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
 	.shift		= 32,
 	.rating		= 150,
-	.cpumask	= CPU_MASK_CPU0,
 	.set_next_event	= clkevt32k_next_event,
 	.set_mode	= clkevt32k_mode,
 };
@@ -197,7 +196,7 @@ void __init at91rm9200_timer_init(void)
 	clkevt.mult = div_sc(AT91_SLOW_CLOCK, NSEC_PER_SEC, clkevt.shift);
 	clkevt.max_delta_ns = clockevent_delta2ns(AT91_ST_ALMV, &clkevt);
 	clkevt.min_delta_ns = clockevent_delta2ns(2, &clkevt) + 1;
-	clkevt.cpumask = cpumask_of_cpu(0);
+	clkevt.cpumask = cpumask_of(0);
 	clockevents_register_device(&clkevt);
 
 	/* register clocksource */