timer: add setup_deferrable_timer macro

Add the trivial missing macro to setup a deferrable timer.
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Acked-by: Thomas Gleixner <tglx@linutronix.de>

include/linux/timer.h

@@ -145,6 +145,8 @@ static inline void init_timer_on_stack_key(struct timer_list *timer,
 
 #define setup_timer(timer, fn, data)					\
 	__setup_timer((timer), (fn), (data), 0)
+#define setup_deferrable_timer(timer, fn, data)				\
+	__setup_timer((timer), (fn), (data), TIMER_DEFERRABLE)
 #define setup_timer_on_stack(timer, fn, data)				\
 	__setup_timer_on_stack((timer), (fn), (data), 0)
 #define setup_deferrable_timer_on_stack(timer, fn, data)		\