udf: Implement adding of dir entries using new iteration code

[ Upstream commit f2844803 ]

Implement function udf_fiiter_add_entry() adding new directory entries
using new directory iteration code.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>