sched/headers: Prepare for new header dependencies before moving code to <linux/sched/wake_q.h>

We are going to split <linux/sched/wake_q.h> out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.

Create a trivial placeholder <linux/sched/wake_q.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.

Include the new header in the files that are going to need it.

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>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

ipc/mqueue.c

@@ -35,6 +35,7 @@
 #include <linux/ipc_namespace.h>
 #include <linux/user_namespace.h>
 #include <linux/slab.h>
+#include <linux/sched/wake_q.h>
 
 #include <net/sock.h>
 #include "util.h"

ipc/msg.c

@@ -31,6 +31,7 @@
 #include <linux/list.h>
 #include <linux/security.h>
 #include <linux/sched.h>
+#include <linux/sched/wake_q.h>
 #include <linux/syscalls.h>
 #include <linux/audit.h>
 #include <linux/seq_file.h>

ipc/sem.c

@@ -82,6 +82,7 @@
 #include <linux/rwsem.h>
 #include <linux/nsproxy.h>
 #include <linux/ipc_namespace.h>
+#include <linux/sched/wake_q.h>
 
 #include <linux/uaccess.h>
 #include "util.h"