softlockup: remove unused definition for spawn_softlockup_task

The definition of spawn_softlockup_task in sched.h became
unnecessary once it was converted to the early_initcall()
interface.

Signed-off-by: Mandeep Singh Baines <[e-mail]>
Signed-off-by: Ingo Molnar <[e-mail]>

include/linux/sched.h

···
 static inline void softlockup_tick(void)
 {
 }
-static inline void spawn_softlockup_task(void)
-{
-}
 static inline void touch_softlockup_watchdog(void)
 {
 }