net: ag71xx: add missed clk_disable_unprepare in error path of probe

The ag71xx_mdio_probe() forgets to call clk_disable_unprepare() when
of_reset_control_get_exclusive() failed. Add the missed call to fix it.

Fixes: d51b6ce4 ("net: ethernet: add ag71xx driver")
Reported-by: NHulk Robot <hulkci@huawei.com>
Signed-off-by: NHuang Guobin <huangguobin4@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/atheros/ag71xx.c

@@ -556,7 +556,8 @@ static int ag71xx_mdio_probe(struct ag71xx *ag)
 	ag->mdio_reset = of_reset_control_get_exclusive(np, "mdio");
 	if (IS_ERR(ag->mdio_reset)) {
 		netif_err(ag, probe, ndev, "Failed to get reset mdio.\n");
-		return PTR_ERR(ag->mdio_reset);
+		err = PTR_ERR(ag->mdio_reset);
+		goto mdio_err_put_clk;
 	}
 
 	mii_bus->name = "ag71xx_mdio";