udf: Convert udf_get_parent() to new directory iteration code

[ Upstream commit 9b06fbef ]

Convert udf_get_parent() to use udf_fiiter_find_entry().

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>