ARM: localtimer: clean up local timer on hot unplug

When a CPU is hot unplugged, the generic tick code cleans up the
clock event device, but fails to call down to the device's set_mode
function to actually shut the device down.

To work around this, we've historically had a local_timer_stop()
callback out of the hotplug code.  However, this adds needless
complexity when we have the clock event device itself available.

Explicitly call the clock event device's set_mode function with
CLOCK_EVT_MODE_UNUSED, so that the hardware can be cleanly shutdown
without any special external callbacks.  When/if the generic code
is fixed, percpu_timer_stop() can be killed off.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/kernel/smp_twd.c

@@ -150,13 +150,3 @@ void __cpuinit twd_timer_setup(struct clock_event_device *clk)
 
 	clockevents_register_device(clk);
 }
-
-#ifdef CONFIG_HOTPLUG_CPU
-/*
- * take a local timer down
- */
-void twd_timer_stop(void)
-{
-	__raw_writel(0, twd_base + TWD_TIMER_CONTROL);
-}
-#endif