UBIFS: constify file and inode operations

This patch adds 'const' qualifier to UBIFS xattr inode and file
operations.
Pointed-out-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

fs/ubifs/xattr.c

@@ -78,9 +78,9 @@ enum {
 	SECURITY_XATTR,
 };
 
-static struct inode_operations none_inode_operations;
+static const struct inode_operations none_inode_operations;
 static struct address_space_operations none_address_operations;
-static struct file_operations none_file_operations;
+static const struct file_operations none_file_operations;
 
 /**
  * create_xattr - create an extended attribute.