scsi: qla2xxx: Rework key encoding in qlt_find_host_by_d_id()

Use the same approach for encoding the destination ID as the approach used
by qlt_update_vp_map().

Cc: Himanshu Madhani <hmadhani@marvell.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Tested-by: Himanshu Madhani <hmadhani@marvell.com>
Reviewed-by: Himanshu Madhani <hmadhani@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>