sched/headers: Make all include/linux/sched/*.h headers build standalone

Make each header self-sufficient, so that it can be built successfully
both in an allnoconfig and allyesconfig kernel.

Also standardize the naming of their header guards.

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/sched/sysctl.h

@@ -1,5 +1,9 @@
-#ifndef _SCHED_SYSCTL_H
-#define _SCHED_SYSCTL_H
+#ifndef _LINUX_SCHED_SYSCTL_H
+#define _LINUX_SCHED_SYSCTL_H
+
+#include <linux/types.h>
+
+struct ctl_table;
 
 #ifdef CONFIG_DETECT_HUNG_TASK
 extern int	     sysctl_hung_task_check_count;
@@ -78,4 +82,4 @@ extern int sysctl_schedstats(struct ctl_table *table, int write,
 				 void __user *buffer, size_t *lenp,
 				 loff_t *ppos);
 
-#endif /* _SCHED_SYSCTL_H */
+#endif /* _LINUX_SCHED_SYSCTL_H */