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/ext4/file.c b/fs/ext4/file.c
index 5ca3eca..9630583 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -81,7 +81,7 @@
 	return generic_file_aio_write(iocb, iov, nr_segs, pos);
 }
 
-static struct vm_operations_struct ext4_file_vm_ops = {
+static const struct vm_operations_struct ext4_file_vm_ops = {
 	.fault		= filemap_fault,
 	.page_mkwrite   = ext4_page_mkwrite,
 };