sched/headers: Prepare for new header dependencies before moving code to <linux/sched/autogroup.h>

We are going to split <linux/sched/autogroup.h> out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.

Create a trivial placeholder <linux/sched/autogroup.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.

Include the new header in the files that are going to need it.

Acked-by: Linus Torvalds <[e-mail]>
Cc: Mike Galbraith <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: [e-mail]
Signed-off-by: Ingo Molnar <[e-mail]>

fs/proc/base.c

···
 #include <linux/user_namespace.h>
 #include <linux/fs_struct.h>
 #include <linux/slab.h>
+#include <linux/sched/autogroup.h>
 #include <linux/flex_array.h>
 #include <linux/posix-timers.h>
 #ifdef CONFIG_HARDWALL

include/linux/sched/autogroup.h

···
+#ifndef _LINUX_SCHED_AUTOGROUP_H
+#define _LINUX_SCHED_AUTOGROUP_H
+
+#include <linux/sched.h>
+
+#endif /* _LINUX_SCHED_AUTOGROUP_H */

kernel/exit.c

···
 
 #include <linux/mm.h>
 #include <linux/slab.h>
+#include <linux/sched/autogroup.h>
 #include <linux/interrupt.h>
 #include <linux/module.h>
 #include <linux/capability.h>

kernel/fork.c

···
  */
 
 #include <linux/slab.h>
+#include <linux/sched/autogroup.h>
 #include <linux/init.h>
 #include <linux/unistd.h>
 #include <linux/module.h>

kernel/sched/autogroup.h

···
 
 #include <linux/kref.h>
 #include <linux/rwsem.h>
+#include <linux/sched/autogroup.h>
 
 struct autogroup {
 	/*

kernel/sys.c

···
 #include <linux/binfmts.h>
 
 #include <linux/sched.h>
+#include <linux/sched/autogroup.h>
 #include <linux/sched/loadavg.h>
 #include <linux/rcupdate.h>
 #include <linux/uidgid.h>