zedboard-zynq7: Fix DTS Network PHY node

* Fix-up the Ethernet PHY node handle in the device-tree
* This resolves the issue where the kernel will fail to correctly probe
  the PHY

Signed-off-by: Nathan Rossi <nathan.rossi@xilinx.com>
zynq-7-base.dtsi: Fix-up register mapping

* Fix-up the register mapping of the dev-cfg node which overlaps the
  register space of the xadc node

Signed-off-by: Nathan Rossi <nathan.rossi@xilinx.com>