net: phy: aquantia: readd XGMII support for AQR107

XGMII interface mode no longer works on AQR107 after the recent changes,
adding back support.

Fixes: 570c8a7d ("net: phy: aquantia: check for supported interface modes in config_init")
Signed-off-by: Madalin Bucur <madalin.bucur@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>