ARM: dts: kirkwood: Add address to ethernet-phy unit name

PHYs have an address on the mdio bus. So the unit name should contain
an address. This is complicated in that some .dtsi files contain the
node, but the reg is set in the .dts file. In this case, use the
abstract address X.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>