const: make block_device_operations const

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/s390/block/dasd_int.h b/drivers/s390/block/dasd_int.h
index 5e47a1e..8afd9fa 100644
--- a/drivers/s390/block/dasd_int.h
+++ b/drivers/s390/block/dasd_int.h
@@ -540,7 +540,7 @@
 extern debug_info_t *dasd_debug_area;
 extern struct dasd_profile_info_t dasd_global_profile;
 extern unsigned int dasd_profile_level;
-extern struct block_device_operations dasd_device_operations;
+extern const struct block_device_operations dasd_device_operations;
 
 extern struct kmem_cache *dasd_page_cache;