scsi: hisi_sas: Snapshot HW cache of IOST and ITCT at debugfs

The value of IOST/ITCT is updated to cache first, and then synchronize to
DDR periodically. So the value in IOST/ITCT cache is the latest data and
it's important for debugging.

So, the HW cache of IOST and ITCT should be snapshot at debugfs.

Signed-off-by: Luo Jiaxing <luojiaxing@huawei.com>
Signed-off-by: John Garry <john.garry@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>