ibm_newemac: Fix ZMII refcounting bug

When using ZMII for MDIO only (such as 440GX with RGMII for data and ZMII for
MDIO), the ZMII code would fail to properly refcount, thus triggering a
BUG_ON().

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Stefan Roese <sr@denx.de>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

drivers/net/ibm_newemac/zmii.c

@@ -83,12 +83,14 @@ int __devinit zmii_attach(struct of_device *ofdev, int input, int *mode)
 
 	ZMII_DBG(dev, "init(%d, %d)" NL, input, *mode);
 
-	if (!zmii_valid_mode(*mode))
+	if (!zmii_valid_mode(*mode)) {
 		/* Probably an EMAC connected to RGMII,
 		 * but it still may need ZMII for MDIO so
 		 * we don't fail here.
 		 */
+		dev->users++;
 		return 0;
+	}
 
 	mutex_lock(&dev->lock);