Doh, I completely missed that devices marked DUMMY are not running
the set_mode function. So we force broadcasting, but we keep the
local APIC timer running.

Let the clock event layer mark the device _after_ switching it off.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>