kill the obsolete thread_group_cputime_free() helper

Kill the empty thread_group_cputime_free() helper.  It was needed to free
the per-cpu data which we no longer have.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Veaceslav Falico <vfalico@redhat.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/sched.h

@@ -2393,10 +2393,6 @@ static inline void thread_group_cputime_init(struct signal_struct *sig)
 	spin_lock_init(&sig->cputimer.lock);
 }
 
-static inline void thread_group_cputime_free(struct signal_struct *sig)
-{
-}
-
 /*
  * Reevaluate whether the task has signals pending delivery.
  * Wake the task if so.

kernel/fork.c

@@ -167,7 +167,6 @@ EXPORT_SYMBOL(free_task);
 
 static inline void free_signal_struct(struct signal_struct *sig)
 {
-	thread_group_cputime_free(sig);
 	kmem_cache_free(signal_cachep, sig);
 }