net: ethernet: cpmac: Call SET_NETDEV_DEV()

The TI CPMAC driver calls into PHYLIB which now checks for
net_device->dev.parent, so make sure we do set it before calling into
any MDIO/PHYLIB related function.

Fixes: ec988ad7

 ("phy: Don't increment MDIO bus refcount unless it's a different owner")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>