scsi: hisi_sas: only reset link for PHY_FUNC_LINK_RESET

We currently do a hard reset for a link reset. Change this to do a link
reset only.

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