net: dp83822: Fix OF_MDIO config check

When CONFIG_OF_MDIO is set to be a module the code block is not
compiled. Use the IS_ENABLED macro that checks for both built in as
well as module.

Fixes: 5dc39fd ("net: phy: DP83822: Add ability to advertise Fiber connection")
Signed-off-by: Johannes Schneider <[email protected]>
Reviewed-by: Maxime Chevallier <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Paolo Abeni <[email protected]>

Author: js731ca

drivers/net/phy/dp83822.c

@@ -730,7 +730,7 @@ static int dp83822_phy_reset(struct phy_device *phydev)
 	return phydev->drv->config_init(phydev);
 }
 
-#ifdef CONFIG_OF_MDIO
+#if IS_ENABLED(CONFIG_OF_MDIO)
 static const u32 tx_amplitude_100base_tx_gain[] = {
 	80, 82, 83, 85, 87, 88, 90, 92,
 	93, 95, 97, 98, 100, 102, 103, 105,