scsi: hisi_sas: relocate clearing ITCT and freeing device

In certain scenarios we may just want to clear the ITCT for a device, and not
free other resources like the SATA bitmap using in v2 hw.

To facilitate this, this patch relocates the code of clearing ITCT from
free_device() to a new hw interface clear_itct().  Then for some hw, we should
not realise free_device() if there's nothing left to do for it.

[mkp: typo]

Signed-off-by: Xiaofei Tan <tanxiaofei@huawei.com>
Signed-off-by: John Garry <john.garry@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>