UBIFS: constify operations

Mark super, file, and inode operation structcutes with 'const'.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
index a7fc97f..53811e5 100644
--- a/fs/ubifs/super.c
+++ b/fs/ubifs/super.c
@@ -1778,7 +1778,7 @@
 	return 0;
 }
 
-struct super_operations ubifs_super_operations = {
+const struct super_operations ubifs_super_operations = {
 	.alloc_inode   = ubifs_alloc_inode,
 	.destroy_inode = ubifs_destroy_inode,
 	.put_super     = ubifs_put_super,