UBI: constify file operations

Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h
index 4a8ec48..381f0e1 100644
--- a/drivers/mtd/ubi/ubi.h
+++ b/drivers/mtd/ubi/ubi.h
@@ -449,9 +449,9 @@
 };
 
 extern struct kmem_cache *ubi_wl_entry_slab;
-extern struct file_operations ubi_ctrl_cdev_operations;
-extern struct file_operations ubi_cdev_operations;
-extern struct file_operations ubi_vol_cdev_operations;
+extern const struct file_operations ubi_ctrl_cdev_operations;
+extern const struct file_operations ubi_cdev_operations;
+extern const struct file_operations ubi_vol_cdev_operations;
 extern struct class *ubi_class;
 extern struct mutex ubi_devices_mutex;