scsi: hisi_sas: add hisi_sas_clear_nexus_ha()

Add function for upper-layer to reset controller when all else fails.

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>