scsi: hisi_sas: move PHY init to hisi_sas_scan_start()

Relocate the PHY init code from LLDD hw init path to
hisi_sas_scan_start().

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>