sched: Move completion code from core.c to completion.c

Completions already have their own header file: linux/completion.h
Move the implementation out of kernel/sched/core.c and into its own
file: kernel/sched/completion.c.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/n/tip-x2y49rmxu5dljt66ai2lcfuw@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/include/linux/completion.h b/include/linux/completion.h
index 3cd574d..22c33e3 100644
--- a/include/linux/completion.h
+++ b/include/linux/completion.h
@@ -5,7 +5,7 @@
  * (C) Copyright 2001 Linus Torvalds
  *
  * Atomic wait-for-completion handler data structures.
- * See kernel/sched/core.c for details.
+ * See kernel/sched/completion.c for details.
  */
 
 #include <linux/wait.h>