net/phy: Correct AR8021 phy_mask

There was wrong phy_mask for AR8021 device,
so the AR8021 can't be probed correctly.
Changed it from 0x4fffff to 0x4ffff0.

Signed-off-by: Haijun Zhang <Haijun.Zhang@freescale.com>

drivers/net/phy/atheros.c

@@ -41,7 +41,7 @@ static int ar8035_config(struct phy_device *phydev)
 static struct phy_driver AR8021_driver =  {
 	.name = "AR8021",
 	.uid = 0x4dd040,
-	.mask = 0x4fffff,
+	.mask = 0x4ffff0,
 	.features = PHY_GBIT_FEATURES,
 	.config = ar8021_config,
 	.startup = genphy_startup,