net: sun8i-emac: fix printing NULL character

If the variant is not set and therefore NULL, do not attempt to print
the variant.

Signed-off-by: Lothar Felten <lothar.felten@gmail.com>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
Reviewed-by: Jagan Teki <jagan@openedev.com>
Tested-by: Jagan Teki <jagan@openedev.com>

drivers/net/sun8i_emac.c

@@ -843,8 +843,7 @@ static int sun8i_emac_eth_ofdata_to_platdata(struct udevice *dev)
 	priv->variant = dev_get_driver_data(dev);
 
 	if (!priv->variant) {
-		printf("%s: Missing variant '%s'\n", __func__,
-		       (char *)priv->variant);
+		printf("%s: Missing variant\n", __func__);
 		return -EINVAL;
 	}