target: pscsi: Introduce TYPE_ZBC support

TYPE_ZBC host managed zoned block devices are also block devices
despite the non-standard device type (14h). Handle them similarly to
regular TYPE_DISK devices.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>