[SCSI] libsas: use right function to alloc smp response

In fact the disc_resp buffer will be overwrite by smp response, so we never
found this typo, correct it by using the right one.
Signed-off-by: John Gong <john_gong@usish.com>
Signed-off-by: Jack Wang <jack_wang@usish.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

drivers/scsi/libsas/sas_expander.c

@@ -388,7 +388,7 @@ int sas_ex_phy_discover(struct domain_device *dev, int single)
 	if (!disc_req)
 		return -ENOMEM;
 
-	disc_resp = alloc_smp_req(DISCOVER_RESP_SIZE);
+	disc_resp = alloc_smp_resp(DISCOVER_RESP_SIZE);
 	if (!disc_resp) {
 		kfree(disc_req);
 		return -ENOMEM;