[SCSI] pm8001: potential null dereference in pm8001_dev_gone_notify()

In the original code we dereferenced "pm8001_dev" before checking if it
was null. This patch moves the dereference inside the condition.

This was found by a static checker (smatch). I looked, but I couldn't
tell if "pm8001_dev" dev was ever actually null. The approach in this
patch seemed like the safest response.

Signed-off-by: Dan Carpenter <[e-mail]>
Acked-by: Jack Wang <[e-mail]>
Signed-off-by: James Bottomley <[e-mail]>

drivers/scsi/pm8001/pm8001_sas.c

···
 	u32 tag;
 	struct pm8001_hba_info *pm8001_ha;
 	struct pm8001_device *pm8001_dev = dev->lldd_dev;
-	u32 device_id = pm8001_dev->device_id;
+
 	pm8001_ha = pm8001_find_ha_by_dev(dev);
 	spin_lock_irqsave(&pm8001_ha->lock, flags);
 	pm8001_tag_alloc(pm8001_ha, &tag);
 	if (pm8001_dev) {
+		u32 device_id = pm8001_dev->device_id;
+
 		PM8001_DISC_DBG(pm8001_ha,
 			pm8001_printk("found dev[%d:%x] is gone.\n",
 			pm8001_dev->device_id, pm8001_dev->dev_type));