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>
diff --git a/arch/avr32/kernel/time.c b/arch/avr32/kernel/time.c
index 283481d..0ff46bf 100644
--- a/arch/avr32/kernel/time.c
+++ b/arch/avr32/kernel/time.c
@@ -106,7 +106,6 @@
 	.features	= CLOCK_EVT_FEAT_ONESHOT,
 	.shift		= 16,
 	.rating		= 50,
-	.cpumask	= CPU_MASK_CPU0,
 	.set_next_event	= comparator_next_event,
 	.set_mode	= comparator_mode,
 };
@@ -134,6 +133,7 @@
 	comparator.mult = div_sc(counter_hz, NSEC_PER_SEC, comparator.shift);
 	comparator.max_delta_ns = clockevent_delta2ns((u32)~0, &comparator);
 	comparator.min_delta_ns = clockevent_delta2ns(50, &comparator) + 1;
+	comparator.cpumask = cpumask_of(0);
 
 	sysreg_write(COMPARE, 0);
 	timer_irqaction.dev_id = &comparator;