Fix error checking in Vitesse IRQ config

phy_read() returns a negative number if there's an error, but the
error-checking code in the Vitesse driver's config_intr function
triggers if phy_read() returns non-zero.  Correct that.

Signed-off-by: Andy Fleming <afleming@freescale.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

drivers/net/phy/vitesse.c

@@ -109,7 +109,7 @@ static int vsc824x_config_intr(struct phy_device *phydev)
 		 */
 		err = phy_read(phydev, MII_VSC8244_ISTAT);
 
-		if (err)
+		if (err < 0)
 			return err;
 
 		err = phy_write(phydev, MII_VSC8244_IMASK, 0);