DTS: Do not add addition "ranges" to axi/xps_epc

It already uses compound slave to generate empty "ranges" property to
axi/xps_epc. Should not add one more empty "ranges".

Signed-off-by: Wendy Liang <jliang@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Acked-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>