scsi: hisi_sas: complete all tasklets prior to host reset

The CQ event is handled in tasklet context, and it could be delayed if
the system loading is high.

It is possible to run into some problems when executing a host reset
when cq_tasklet_vx_hw() is being executed.

So, prior to host reset, execute tasklet_kill() to ensure that all CQ
tasklets are complete.

Besides, as the function hisi_sas_wait_tasklets_done() is added to do
tasklet_kill(), this patch refactors some code where tasklet_kill() is
used.

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>
diff --git a/drivers/scsi/hisi_sas/hisi_sas.h b/drivers/scsi/hisi_sas/hisi_sas.h
index c65d151..c5fd545 100644
--- a/drivers/scsi/hisi_sas/hisi_sas.h
+++ b/drivers/scsi/hisi_sas/hisi_sas.h
@@ -426,4 +426,5 @@ extern void hisi_sas_slot_task_free(struct hisi_hba *hisi_hba,
 				    struct hisi_sas_slot *slot);
 extern void hisi_sas_init_mem(struct hisi_hba *hisi_hba);
 extern void hisi_sas_rst_work_handler(struct work_struct *work);
+extern void hisi_sas_kill_tasklets(struct hisi_hba *hisi_hba);
 #endif