mm/sparse-vmemmap.c: make sure init_mm is included

mm/sparse-vmemmap.c uses init_mm in some places.  However, it is not
present in any of the headers currently included in the file.

init_mm is defined as extern in sched.h, so we add it to the headers list

Up to now, this problem was masked by the fact that functions like
set_pte_at() and pmd_populate_kernel() are usually macros that expand to
simpler variants that does not use the first parameter at all.
Signed-off-by: NGlauber de Oliveira Costa <gcosta@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/sparse-vmemmap.c

@@ -24,6 +24,7 @@
 #include <linux/module.h>
 #include <linux/spinlock.h>
 #include <linux/vmalloc.h>
+#include <linux/sched.h>
 #include <asm/dma.h>
 #include <asm/pgalloc.h>
 #include <asm/pgtable.h>