const: mark struct vm_struct_operations

* mark struct vm_area_struct::vm_ops as const
* mark vm_ops in AGP code

But leave TTM code alone, something is fishy there with global vm_ops
being used.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 21d6aa4..84a524a 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -171,7 +171,7 @@
 	struct anon_vma *anon_vma;	/* Serialized by page_table_lock */
 
 	/* Function pointers to deal with this struct. */
-	struct vm_operations_struct * vm_ops;
+	const struct vm_operations_struct *vm_ops;
 
 	/* Information about our backing store: */
 	unsigned long vm_pgoff;		/* Offset (within vm_file) in PAGE_SIZE