ARM: zynq: DT: Use the zynq binding with macb

Use the new zynq binding for macb ethernet, since it will disable half
duplex gigabit like the Zynq TRM says to do. Also allow the compatible
cadence gem binding that won't disable half duplex but works otherwise.

Signed-off-by: Nathan Sullivan <nathan.sullivan@ni.com>
Acked-by: Sören Brinkmann <soren.brinkmann@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>