net: phy: aquantia: use genphy_c45_read_status

Use new function genphy_c45_read_status(). 1000BaseT link partner
advertisement needs to be read from vendor registers.

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