struct tick_shed uses struct hrtimer, explictly include the right header file.

preemtivly fixes the following warning
  CC      arch/powerpc/platforms/iseries/setup.o
In file included from arch/powerpc/platforms/iseries/setup.c:30:
include/linux/tick.h:45: error: field 'sched_timer' has incomplete type

Signed-off-by: Tony Breeds <redacted>

---

 include/linux/tick.h |    1 +
 1 file changed, 1 insertion(+)

Index: working/include/linux/tick.h
===================================================================

--- working.orig/include/linux/tick.h
+++ working/include/linux/tick.h

@@ -7,6 +7,7 @@
 #define _LINUX_TICK_H
 
 #include <linux/clockchips.h>
+#include <linux/hrtimer.h>
 
 #ifdef CONFIG_GENERIC_CLOCKEVENTS