drivers: net: phy: at803x: Add missing mdio device id

at803x supports Atheros 8030, 8031 and 8035 PHYs. 8031 was missing from
the mdio device id table.
Signed-off-by: NHelmut Schaa <helmut.schaa@googlemail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/phy/at803x.c

@@ -217,6 +217,7 @@ module_exit(atheros_exit);
 
 static struct mdio_device_id __maybe_unused atheros_tbl[] = {
 	{ 0x004dd076, 0xffffffef },
+	{ 0x004dd074, 0xffffffef },
 	{ 0x004dd072, 0xffffffef },
 	{ }
 };