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/gpu/drm/radeon/radeon_ttm.c b/drivers/gpu/drm/radeon/radeon_ttm.c
index acd889c..5b1cf04a 100644
--- a/drivers/gpu/drm/radeon/radeon_ttm.c
+++ b/drivers/gpu/drm/radeon/radeon_ttm.c
@@ -530,7 +530,7 @@
 }
 
 static struct vm_operations_struct radeon_ttm_vm_ops;
-static struct vm_operations_struct *ttm_vm_ops = NULL;
+static const struct vm_operations_struct *ttm_vm_ops = NULL;
 
 static int radeon_ttm_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 {