timer: Initialize the field slack of timer_list

TIMER_INITIALIZER() should initialize the field slack of timer_list as
__init_timer() does.

Signed-off-by: Changli Gao <xiaosuo@gmail.com>
Cc: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

include/linux/timer.h

diff --git a/include/linux/timer.h b/include/linux/timer.h
index f3dccdb..1794674 100644
--- a/include/linux/timer.h
+++ b/include/linux/timer.h
@@ -54,6 +54,7 @@
 		.expires = (_expires),				\
 		.data = (_data),				\
 		.base = &boot_tvec_bases,			\
+		.slack = -1,					\
 		__TIMER_LOCKDEP_MAP_INITIALIZER(		\
 			__FILE__ ":" __stringify(__LINE__))	\
 	}