ARM: smp_twd: make local_timer_stop a symbol instead of a #define

When CONFIG_HAVE_ARM_TWD is selected, local_timer_stop is a #define,
while all other local timers are using a real function.

Convert it to an alias of twd_timer_stop, as it helps converting
all local timers to another internal API in a sane way.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

arch/arm/include/asm/localtimer.h

@@ -26,17 +26,13 @@ void percpu_timer_setup(void);
 
 #include "smp_twd.h"
 
-#define local_timer_stop(c)	twd_timer_stop((c))
-
-#else
+#endif
 
 /*
  * Stop the local timer
  */
 void local_timer_stop(struct clock_event_device *);
 
-#endif
-
 /*
  * Setup a local timer interrupt for a CPU.
  */