net: phy: marvell10g: improve mv3310_config_aneg

Now that genphy_c45_pma_setup_forced() makes sure the "aneg enabled"
bit is cleared, the call to genphy_c45_an_disable_aneg() isn't needed
any longer. And the code pattern is now the same as in
genphy_config_aneg().

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>