drbd: Constify struct file_operations

Signed-off-by: Emese Revfy <re.emese@gmail.com>
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 157d1e4..af30ca9 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -151,7 +151,7 @@
 
 DEFINE_RATELIMIT_STATE(drbd_ratelimit_state, 5 * HZ, 5);
 
-static struct block_device_operations drbd_ops = {
+static const struct block_device_operations drbd_ops = {
 	.owner =   THIS_MODULE,
 	.open =    drbd_open,
 	.release = drbd_release,