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

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

Include kernel.h and atomic.h.

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]>
Cc: [e-mail]
Signed-off-by: Ingo Molnar <[e-mail]>

include/linux/sched/mm.h

···
 #ifndef _LINUX_SCHED_MM_H
 #define _LINUX_SCHED_MM_H
 
+#include <linux/kernel.h>
+#include <linux/atomic.h>
 #include <linux/sched.h>
 #include <linux/mm_types.h>
 #include <linux/gfp.h>