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/arm/mach-msm/timer.c b/arch/arm/mach-msm/timer.c
index 345a14c..444d9c0 100644
--- a/arch/arm/mach-msm/timer.c
+++ b/arch/arm/mach-msm/timer.c
@@ -182,7 +182,7 @@
 			clockevent_delta2ns(0xf0000000 >> clock->shift, ce);
 		/* 4 gets rounded down to 3 */
 		ce->min_delta_ns = clockevent_delta2ns(4, ce);
-		ce->cpumask = cpumask_of_cpu(0);
+		ce->cpumask = cpumask_of(0);
 
 		cs->mult = clocksource_hz2mult(clock->freq, cs->shift);
 		res = clocksource_register(cs);