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

We are going to split <linux/sched/coredump.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/coredump.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>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 71e3ded..dee92fa 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -9,6 +9,7 @@
 
 #include <linux/mm.h>
 #include <linux/sched.h>
+#include <linux/sched/coredump.h>
 #include <linux/highmem.h>
 #include <linux/hugetlb.h>
 #include <linux/mmu_notifier.h>
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 212a2af..ba40b7f 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -3,6 +3,7 @@
 #include <linux/mm.h>
 #include <linux/sched.h>
 #include <linux/sched/mm.h>
+#include <linux/sched/coredump.h>
 #include <linux/mmu_notifier.h>
 #include <linux/rmap.h>
 #include <linux/swap.h>
diff --git a/mm/ksm.c b/mm/ksm.c
index 5632c9d..19b4f2d 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -20,6 +20,7 @@
 #include <linux/mman.h>
 #include <linux/sched.h>
 #include <linux/sched/mm.h>
+#include <linux/sched/coredump.h>
 #include <linux/rwsem.h>
 #include <linux/pagemap.h>
 #include <linux/rmap.h>
diff --git a/mm/memory.c b/mm/memory.c
index b0495ec..6fc918b 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -41,6 +41,7 @@
 #include <linux/kernel_stat.h>
 #include <linux/mm.h>
 #include <linux/sched/mm.h>
+#include <linux/sched/coredump.h>
 #include <linux/hugetlb.h>
 #include <linux/mman.h>
 #include <linux/swap.h>
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index d289366..69f75b0 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -23,6 +23,7 @@
 #include <linux/gfp.h>
 #include <linux/sched.h>
 #include <linux/sched/mm.h>
+#include <linux/sched/coredump.h>
 #include <linux/swap.h>
 #include <linux/timex.h>
 #include <linux/jiffies.h>