sched/headers: Prepare to move 'init_task' and 'init_thread_union' from <linux/sched.h> to <linux/sched/task.h>

Update all usage sites first.

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>
diff --git a/mm/vmacache.c b/mm/vmacache.c
index 4355d34..7ffa0ee 100644
--- a/mm/vmacache.c
+++ b/mm/vmacache.c
@@ -2,6 +2,7 @@
  * Copyright (C) 2014 Davidlohr Bueso.
  */
 #include <linux/sched/signal.h>
+#include <linux/sched/task.h>
 #include <linux/mm.h>
 #include <linux/vmacache.h>