net: phy: dp83822: fix transmit amplitude if CONFIG_OF_MDIO not defined

When CONFIG_OF_MDIO is not defined the index for selecting the transmit
amplitude voltage for 100BASE-TX is set to 0, but it should be -1, if there
is no need to modify the transmit amplitude voltage. Move initialization of
the index from dp83822_of_init to dp8382x_probe.

Fixes: 4f3735e ("net: phy: dp83822: Add support for changing the transmit amplitude voltage")
Reviewed-by: Gerhard Engleder <[email protected]>
Signed-off-by: Dimitri Fedrau <[email protected]>
Link: https://patch.msgid.link/20250317-dp83822-fix-transceiver-mdio-v2-1-fb09454099a4@liebherr.com
Signed-off-by: Jakub Kicinski <[email protected]>

Author: DimitriFedrau

drivers/net/phy/dp83822.c

@@ -833,7 +833,6 @@ static int dp83822_of_init(struct phy_device *phydev)
 		dp83822->set_gpio2_clk_out = true;
 	}
 
-	dp83822->tx_amplitude_100base_tx_index = -1;
 	ret = phy_get_tx_amplitude_gain(phydev, dev,
 					ETHTOOL_LINK_MODE_100baseT_Full_BIT,
 					&val);
@@ -931,6 +930,7 @@ static int dp8382x_probe(struct phy_device *phydev)
 	if (!dp83822)
 		return -ENOMEM;
 
+	dp83822->tx_amplitude_100base_tx_index = -1;
 	phydev->priv = dp83822;
 
 	return 0;