libata-link: update ata_scsi_error() to handle PMP links

Update ata_scsi_error() to handle PMP links.  As error conditions can
occur on both host and PMP links, __ata_port_for_each_link() is used.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>