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/include/asm/smp_twd.h

@@ -22,7 +22,6 @@ struct clock_event_device;
 
 extern void __iomem *twd_base;
 
-void twd_timer_stop(void);
 int twd_timer_ack(void);
 void twd_timer_setup(struct clock_event_device *);