sched/headers: Remove <linux/sched.h> from <linux/sched/hotplug.h>

The <linux/sched/hotplug.h> file is a self-contained header and users of
it either don't need <linux/sched.h> - or have already included it.

This reduces the size of the header dependency graph.

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

include/linux/sched/hotplug.h

···
 #ifndef _LINUX_SCHED_HOTPLUG_H
 #define _LINUX_SCHED_HOTPLUG_H
 
-#include <linux/sched.h>
-
 /*
  * Scheduler interfaces for hotplug CPU support:
  */