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/dir.c b/fs/ubifs/dir.c
index f448ab1..d29b771 100644
--- a/fs/ubifs/dir.c
+++ b/fs/ubifs/dir.c
@@ -1199,7 +1199,7 @@
 	return 0;
 }
 
-struct inode_operations ubifs_dir_inode_operations = {
+const struct inode_operations ubifs_dir_inode_operations = {
 	.lookup      = ubifs_lookup,
 	.create      = ubifs_create,
 	.link        = ubifs_link,
@@ -1219,7 +1219,7 @@
 #endif
 };
 
-struct file_operations ubifs_dir_operations = {
+const struct file_operations ubifs_dir_operations = {
 	.llseek         = ubifs_dir_llseek,
 	.release        = ubifs_dir_release,
 	.read           = generic_read_dir,