ARM: dts: imx53-tx53: Fix 'ethernet-phy@0' node with unit name and no reg property

The following build warning is seen with W=1:

Warning (unit_address_vs_reg): Node /soc/aips@60000000/ethernet@63fec000/ethernet-phy@0 has a unit name, but no reg property

Fix this warning by adding reg property from such node and, consequently,
includes a mdio node into the fec node, with the 'address-cells' and
'size-cells' to avoid these other following warnings:

Warning (reg_format): "reg" property in /soc/aips@60000000/ethernet@63fec000/ethernet-phy@0 has invalid length (4 bytes) (#address-cells == 2, #size-cells == 1)
Warning (avoid_default_addr_size): Relying on default #address-cells value for /soc/aips@60000000/ethernet@63fec000/ethernet-phy@0
Warning (avoid_default_addr_size): Relying on default #size-cells value for /soc/aips@60000000/ethernet@63fec000/ethernet-phy@0

Signed-off-by: Marco Franchi <marco.franchi@nxp.com>
Tested-by: Lothar Waßmann <LW@karo-electronics.de>
Acked-by: Lothar Waßmann <LW@karo-electronics.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>