net: dsa: mv88e6060: Replace ds with priv

Pass around priv, not ds. This will help with changing to an mdio
driver, and makes this driver more like mv88e6xxx.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>