net: phy: aquantia: check for supported interface modes in config_init

Let config_init check for unsupported interface modes on AQR107/AQCS109.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
[hkallweit1@gmail.com: adjusted for AQR107/AQCS109 specifics]
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>