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>
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 2d1e1a1..dd597d8 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2393,10 +2393,6 @@
 	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.
diff --git a/kernel/fork.c b/kernel/fork.c
index e08e301..58f8611 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -167,7 +167,6 @@
 
 static inline void free_signal_struct(struct signal_struct *sig)
 {
-	thread_group_cputime_free(sig);
 	kmem_cache_free(signal_cachep, sig);
 }