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/drivers/clocksource/tcb_clksrc.c b/drivers/clocksource/tcb_clksrc.c
index f450588..254f106 100644
--- a/drivers/clocksource/tcb_clksrc.c
+++ b/drivers/clocksource/tcb_clksrc.c
@@ -154,7 +154,6 @@
 		.shift		= 32,
 		/* Should be lower than at91rm9200's system timer */
 		.rating		= 125,
-		.cpumask	= CPU_MASK_CPU0,
 		.set_next_event	= tc_next_event,
 		.set_mode	= tc_mode,
 	},
@@ -195,6 +194,7 @@
 	clkevt.clkevt.max_delta_ns
 		= clockevent_delta2ns(0xffff, &clkevt.clkevt);
 	clkevt.clkevt.min_delta_ns = clockevent_delta2ns(1, &clkevt.clkevt) + 1;
+	clkevt.clkevt.cpumask = cpumask_of(0);
 
 	setup_irq(irq, &tc_irqaction);