scsi: mvsas: mv_sas.c: Fix for possible null pointer dereference

There is otherwise a risk of a possible null pointer dereference.

Was largely found by using a static code analysis program called cppcheck.
Signed-off-by: Rickard Strandqvist <rickard_strandqvist@spectrumdigital.se>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/scsi/mvsas/mv_sas.c

@@ -1344,19 +1344,23 @@ void mvs_dev_gone_notify(struct domain_device *dev)
 {
 	unsigned long flags = 0;
 	struct mvs_device *mvi_dev = dev->lldd_dev;
-	struct mvs_info *mvi = mvi_dev->mvi_info;
+	struct mvs_info *mvi;
+
+	if (!mvi_dev) {
+		mv_dprintk("found dev has gone.\n");
+		return;
+	}
+
+	mvi = mvi_dev->mvi_info;
 
 	spin_lock_irqsave(&mvi->lock, flags);
 
-	if (mvi_dev) {
 	mv_dprintk("found dev[%d:%x] is gone.\n",
 		mvi_dev->device_id, mvi_dev->dev_type);
 	mvs_release_task(mvi, dev);
 	mvs_free_reg_set(mvi, mvi_dev);
 	mvs_free_dev(mvi_dev);
-	} else {
-		mv_dprintk("found dev has gone.\n");
-	}
+
 	dev->lldd_dev = NULL;
 	mvi_dev->sas_device = NULL;