hsr/prp: return error to ip link if MAC address doesn't match for slaves

For offloaded case, if MAC address of the slaves does't match return
an error code to the user space instead of silently failing. Also
print an error message indicating the same.

Signed-off-by: Murali Karicheri <m-karicheri2@ti.com>

net/hsr-prp/hsr_prp_device.c

@@ -996,8 +996,12 @@ int hsr_prp_dev_finalize(struct net_device *hsr_prp_dev,
 	 */
 	if (priv->rx_offloaded &&
 	    !ether_addr_equal(slave[0]->dev_addr,
-			      slave[1]->dev_addr))
+			      slave[1]->dev_addr)) {
+		netdev_err(hsr_prp_dev,
+			   "Slave's MAC addr must be same. So change it\n");
+		res = -EINVAL;
 		goto fail;
+	}
 
 	res = hsr_prp_create_procfs(priv, hsr_prp_dev);
 	if (res)