scsi: hisi_sas: add to_hisi_sas_port()

Introduce function to get hisi_sas_port from asd_sas_port.

Signed-off-by: John Garry <john.garry@huawei.com>
Signed-off-by: Xiang Chen <chenxiang66@hisilicon.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>