PHY: DP83867: Remove looking in parent device for OF properties

Device tree properties for a phy device are expected to be in the phy
node. The current code for the DP83867 also tries to look in the
parent node. The devices binding documentation does not mention this,
no current device tree file makes use of this, and it is not behaviour
we want. So remove looking in the parent device.

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