net: lpc_eth: parse phy nodes from device tree

When connected to a micrel phy, phy_find_first doesn't work properly
because the first phy found is on address 0, the broadcast address but, the
first thing the phy driver is doing is disabling this broadcast address.
The phy is then available only on address 1 but the mdio driver doesn't
know about it.

Instead, register the mdio bus using of_mdiobus_register and try to find
the phy description in device tree before falling back to phy_find_first.

This ultimately also allows to describe the interrupt the phy is connected
to.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>