sched/headers: Prepare to move exit_files() and exit_itimers() from <linux/sched.h> to <linux/sched/task.h>

But first update the usage site.

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/time/posix-timers.c

@@ -35,6 +35,7 @@
 #include <linux/slab.h>
 #include <linux/time.h>
 #include <linux/mutex.h>
+#include <linux/sched/task.h>
 
 #include <linux/uaccess.h>
 #include <linux/list.h>