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/drivers/misc/sgi-gru/grutables.h b/drivers/misc/sgi-gru/grutables.h
index 34ab3d4..46990bc 100644
--- a/drivers/misc/sgi-gru/grutables.h
+++ b/drivers/misc/sgi-gru/grutables.h
@@ -624,7 +624,7 @@
  */
 struct gru_unload_context_req;
 
-extern struct vm_operations_struct gru_vm_ops;
+extern const struct vm_operations_struct gru_vm_ops;
 extern struct device *grudev;
 
 extern struct gru_vma_data *gru_alloc_vma_data(struct vm_area_struct *vma,