net: lan743x: Use correct variable in lan743x_sgmii_config()

There is a copy and paste bug in lan743x_sgmii_config() so it checks
if (ret < 0) instead of if (mii_ctl < 0).

Fixes: 46b777ad ("net: lan743x: Add support to SGMII 1G and 2.5G")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/YrRry7K66BzKezl8@kiliSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/microchip/lan743x_main.c

@@ -1212,8 +1212,8 @@ static int lan743x_sgmii_config(struct lan743x_adapter *adapter)
 
 	/* SGMII/1000/2500BASE-X PCS power down */
 	mii_ctl = lan743x_sgmii_read(adapter, MDIO_MMD_VEND2, MII_BMCR);
-	if (ret < 0)
-		return ret;
+	if (mii_ctl < 0)
+		return mii_ctl;
 
 	mii_ctl |= BMCR_PDOWN;
 	ret = lan743x_sgmii_write(adapter, MDIO_MMD_VEND2, MII_BMCR, mii_ctl);