net: macb: remove redundant struct phy_device declaration

While moving the chunk of code during 739de9a1


("net: macb: Reorganize macb_mii bringup"), the declaration of
struct phy_device declaration was kept. It's not useful in this
function as we alrady have a phydev pointer.

Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>