net: pxa168_eth: Remove HW auto-negotiaion

Marvell Ethernet IP supports PHY negotiation driven by HW. This
fundamentally clashes with libphy (software) driven negotiation and
also cannot cope with quirky PHYs. Therefore, always disable any HW
negotiation features and properly use libphy's phy_device.

Tested-by: Antoine Ténart <antoine.tenart@free-electrons.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>