scsi: hisi_sas: Fix the code logic issue of NULL pointer check about sas_port...

scsi: hisi_sas: Fix the code logic issue of NULL pointer check about sas_port in func:hisi_sas_task_prep

sas_port is a pointer passed by device->port,it accept non-zero check
before running ahead to prevent a null pointer to be passed on.

but some logic issue exist here that sas_port(device->port) was used before
non-zero check,such as func: dev_to_hisi_hba lay on line 290

290 struct hisi_hba #hisi_hba = dev_to_hisi_hba(device)
                                    ^
The code of function:dev_to_hisi_hib is as blow:

return device->port->ha->lldd_ha;

Obviously,device->port is used before non-zero check for non-zero check
begin at line 303 but dev_to_hisi_hba lay on line 290;

so,to fix this bug,I need to shift some code and make sure sas_port
which was used after non-zero check.
Signed-off-by: Nluojiaxing <luojiaxing@huawei.com>
Signed-off-by: NJohn Garry <john.garry@huawei.com>

drivers/scsi/hisi_sas/hisi_sas_main.c

@@ -303,13 +303,13 @@ static int hisi_sas_task_prep(struct sas_task *task,
 			      int *pass)
 {
 	struct domain_device *device = task->dev;
-	struct hisi_hba *hisi_hba = dev_to_hisi_hba(device);
+	struct hisi_hba *hisi_hba;
 	struct hisi_sas_device *sas_dev = device->lldd_dev;
 	struct hisi_sas_port *port;
 	struct hisi_sas_slot *slot;
 	struct hisi_sas_cmd_hdr	*cmd_hdr_base;
 	struct asd_sas_port *sas_port = device->port;
-	struct device *dev = hisi_hba->dev;
+	struct device *dev;
 	int dlvry_queue_slot, dlvry_queue, rc, slot_idx;
 	int n_elem = 0, n_elem_req = 0, n_elem_resp = 0;
 	struct hisi_sas_dq *dq;
@@ -330,6 +330,9 @@ static int hisi_sas_task_prep(struct sas_task *task,
 		return -ECOMM;
 	}
 
+	hisi_hba = dev_to_hisi_hba(device);
+	dev = hisi_hba->dev;
+
 	if (DEV_IS_GONE(sas_dev)) {
 		if (sas_dev)
 			dev_info(dev, "task prep: device %d not ready\n",