udf: Convert udf_link() to new directory iteration code

[ Upstream commit dbfb102d ]

Convert udf_link() to use new directory iteration code for adding entry
into the directory.

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>