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/fs/gfs2/file.c b/fs/gfs2/file.c
index 166f38f..4eb308a 100644
--- a/fs/gfs2/file.c
+++ b/fs/gfs2/file.c
@@ -418,7 +418,7 @@
 	return ret;
 }
 
-static struct vm_operations_struct gfs2_vm_ops = {
+static const struct vm_operations_struct gfs2_vm_ops = {
 	.fault = filemap_fault,
 	.page_mkwrite = gfs2_page_mkwrite,
 };