net: phy: remove unnecessary callback settings in C45 drivers

genphy_c45_aneg_done() is used by phylib as fallback for c45 PHY's if
callback aneg_done isn't defined. So we don't have to set this
explicitly. Same for genphy_c45_pma_read_abilities().

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