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 <msb@google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/linux/sched.h

@@ -302,9 +302,6 @@ extern int softlockup_thresh;
 static inline void softlockup_tick(void)
 {
 }
-static inline void spawn_softlockup_task(void)
-{
-}
 static inline void touch_softlockup_watchdog(void)
 {
 }