sched/headers: Move the task_lock()/unlock() APIs to <linux/sched/task.h>

The task_lock()/task_unlock() APIs are not realated to core scheduling,
they are task lifetime APIs, i.e. they belong into <linux/sched/task.h>.

Move them.

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>

kernel/cgroup/cgroup-v1.c

@@ -6,6 +6,7 @@
 #include <linux/delay.h>
 #include <linux/mm.h>
 #include <linux/sched/signal.h>
+#include <linux/sched/task.h>
 #include <linux/slab.h>
 #include <linux/vmalloc.h>
 #include <linux/delayacct.h>

kernel/cgroup/namespace.c

@@ -1,6 +1,6 @@
 #include "cgroup-internal.h"
 
-#include <linux/sched.h>
+#include <linux/sched/task.h>
 #include <linux/slab.h>
 #include <linux/nsproxy.h>
 #include <linux/proc_ns.h>