s6gmac: fix error return code in s6gmac_probe()

Fix to return a negative error code from the error handling
case instead of 0, as returned elsewhere in this function.

Signed-off-by: Wei Yongjun <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/ethernet/s6gmac.c

···
 	mb = mdiobus_alloc();
 	if (!mb) {
 		printk(KERN_ERR DRV_PRMT "error allocating mii bus\n");
+		res = -ENOMEM;
 		goto errmii;
 	}
 	mb->name = "s6gmac_mii";