sched/headers: Move the 'root_task_group' declaration to <linux/sched/autogroup.h>

Also remove the duplicate declaration from <linux/init_task.h>.

( That declaration was originally duplicated for dependency hell reasons,
  but there's no problem including the much smaller <linux/sched/autogroup.h>
  header now, to pick up the right prototype. )

Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

include/linux/init_task.h

@@ -151,8 +151,6 @@ extern struct group_info init_groups;
 
 extern struct cred init_cred;
 
-extern struct task_group root_task_group;
-
 #ifdef CONFIG_CGROUP_SCHED
 # define INIT_CGROUP_SCHED(tsk)						\
 	.sched_task_group = &root_task_group,

include/linux/sched.h

@@ -1707,10 +1707,6 @@ static inline void set_task_cpu(struct task_struct *p, unsigned int cpu)
 extern long sched_setaffinity(pid_t pid, const struct cpumask *new_mask);
 extern long sched_getaffinity(pid_t pid, struct cpumask *mask);
 
-#ifdef CONFIG_CGROUP_SCHED
-extern struct task_group root_task_group;
-#endif /* CONFIG_CGROUP_SCHED */
-
 extern int task_can_switch_user(struct user_struct *up,
 					struct task_struct *tsk);
 

include/linux/sched/autogroup.h

@@ -4,6 +4,7 @@
 #include <linux/sched.h>
 
 struct signal_struct;
+struct task_group;
 struct seq_file;
 
 #ifdef CONFIG_SCHED_AUTOGROUP
@@ -24,4 +25,8 @@ static inline void sched_autogroup_exit(struct signal_struct *sig) { }
 static inline void sched_autogroup_exit_task(struct task_struct *p) { }
 #endif
 
+#ifdef CONFIG_CGROUP_SCHED
+extern struct task_group root_task_group;
+#endif /* CONFIG_CGROUP_SCHED */
+
 #endif /* _LINUX_SCHED_AUTOGROUP_H */