scsi: hisi_sas: disable stash for v3 hw

driver inclusion
category: bugfix
bugzilla: NA
CVE: NA

For v3 hw, stash is enabled to promote performance, but it does little
help for promoting performance according to current test. What's more, it
causes exception for some situations, so disable stash.

Signed-off-by: Xiang Chen <chenxiang66@hisilicon.com>
Signed-off-by: John Garry <john.garry@huawei.com>

Feature or Bugfix:Bugfix

Signed-off-by: chenxiang (M) <chenxiang66@hisilicon.com>
Reviewed-by: huangdaode <huangdaode@hisilicon.com>
Reviewed-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>