net: phy: aquantia: Add some additional phy interfaces

These are documented in the AQR115 register reference. I haven't tested
them, but perhaps they'll be useful to someone.

Signed-off-by: Sean Anderson <sean.anderson@seco.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>