net: phy: genphy_c45_baset1_an_config_aneg: do no set unknown configuration

Do not change default master/slave autoneg configuration if no
changes was requested.

Fixes: 3da8ffd8 ("net: phy: Add 10BASE-T1L support in phy-c45")
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>