net: phy: aquantia: remove false 5G and 10G speed ability for AQCS109

AQCS109 belongs to a family of PHY's where certain members don't
support 5G or 10G. However for all members of the family the chip
reports 10G and 5G capability. Therefore remove the not supported
modes for AQCS109.

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