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/mm/filemap.c b/mm/filemap.c
index 6c84e598..ef169f3 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1611,7 +1611,7 @@
 }
 EXPORT_SYMBOL(filemap_fault);
 
-struct vm_operations_struct generic_file_vm_ops = {
+const struct vm_operations_struct generic_file_vm_ops = {
 	.fault		= filemap_fault,
 };