sched: Remove double declaration of root_task_group

It's already declared in include/linux/sched.h
Signed-off-by: Li Zefan <lizefan@huawei.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/5135A7D8.7000107@huawei.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

kernel/sched/core.c

@@ -6861,6 +6861,10 @@ int in_sched_functions(unsigned long addr)
 }
 
 #ifdef CONFIG_CGROUP_SCHED
+/*
+ * Default task group.
+ * Every task in system belongs to this group at bootup.
+ */
 struct task_group root_task_group;
 LIST_HEAD(task_groups);
 #endif

kernel/sched/sched.h

@@ -179,11 +179,6 @@ struct task_group {
 #define MAX_SHARES	(1UL << 18)
 #endif
 
-/* Default task group.
- *	Every task in system belong to this group at bootup.
- */
-extern struct task_group root_task_group;
-
 typedef int (*tg_visitor)(struct task_group *, void *);
 
 extern int walk_tg_tree_from(struct task_group *from,