Use ACPI "_RST" method to reset the controller, since FLR is not
supported.

Function hisi_sas_stop_phys() is introduced to remove some code
duplication.

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