scsi: hisi_sas: service interrupt ITCT_CLR interrupt in v2 hw

This patch is a fix related to freeing a device in v2 hw driver.

Before, we polled to ITCT CLR interrupt to check if a device is free.

This was error prone, as if the interrupt doesn't occur in 10us, we miss
processing it.

To avoid this situation, service this interrupt and sync the event with
a completion.

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>