net/fsl: Make xgmac_mdio read error message useful

Print the device address, the register number and the PHY ID for
which the MDIO read operation failed
Signed-off-by: Shruti Kanetkar <Shruti@Freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/freescale/xgmac_mdio.c

@@ -162,7 +162,9 @@ static int xgmac_mdio_read(struct mii_bus *bus, int phy_id, int regnum)
 
 	/* Return all Fs if nothing was there */
 	if (in_be32(&regs->mdio_stat) & MDIO_STAT_RD_ER) {
-		dev_err(&bus->dev, "MDIO read error\n");
+		dev_err(&bus->dev,
+			"Error while reading PHY%d reg at %d.%d\n",
+			phy_id, dev_addr, regnum);
 		return 0xffff;
 	}