mm: include <linux/huge_mm.h> for is_vma_temporary_stack

Include <linux/huge_mm.h> for the definition of is_vma_temporary_stack
to fix the following sparse warning:

  mm/rmap.c:1673:6: warning: symbol 'is_vma_temporary_stack' was not declared. Should it be static?

Link: http://lkml.kernel.org/r/20191009151155.27763-1-ben.dooks@codethink.co.uk
Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Reviewed-by: Qian Cai <cai@lca.pw>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/rmap.c

@@ -61,6 +61,7 @@
 #include <linux/mmu_notifier.h>
 #include <linux/migrate.h>
 #include <linux/hugetlb.h>
+#include <linux/huge_mm.h>
 #include <linux/backing-dev.h>
 #include <linux/page_idle.h>
 #include <linux/memremap.h>