thp: extract khugepaged from mm/huge_memory.c

khugepaged implementation grew to the point when it deserve separate
file in source.

Let's move it to mm/khugepaged.c.

Link: http://lkml.kernel.org/r/1466021202-61880-32-git-send-email-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 7b7406e..92ce91c 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -41,6 +41,16 @@
 #endif
 };
 
+struct kobject;
+struct kobj_attribute;
+
+extern ssize_t single_hugepage_flag_store(struct kobject *kobj,
+				 struct kobj_attribute *attr,
+				 const char *buf, size_t count,
+				 enum transparent_hugepage_flag flag);
+extern ssize_t single_hugepage_flag_show(struct kobject *kobj,
+				struct kobj_attribute *attr, char *buf,
+				enum transparent_hugepage_flag flag);
 extern struct kobj_attribute shmem_enabled_attr;
 
 #define HPAGE_PMD_ORDER (HPAGE_PMD_SHIFT-PAGE_SHIFT)