net: xilinx_emacps: Fix mdio name initialization

net: xilinx_emacps: Fix mdio name initialization

We are using this mdio bus description which
requires properly setup additional device level.
lp->mii_bus->id is address of device itself
but ethernet device itself is
of_get_parent(of_get_parent(lp->phy_node));

ps7_ethernet_0: ps7-ethernet@e000b000 {
	mdio {
		#address-cells = <1>;
		#size-cells = <0>;
		phy0: phy@7 {
			compatible = "marvell,88e1111";
			device_type = "ethernet-phy";
			reg = <7>;
		} ;
	} ;
} ;

This patch fix the problem with several emacps drivers.

Reported-by: Peter Crosthwaite <peter.crosthwaite@petalogix.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Tested-by: Peter Crosthwaite <peter.crosthwaite@petalogix.com>
Acked-by: John Linn <john.linn@xilinx.com>