net: zynq_gem: convert to use livetree

This patch updates the zynq gem driver to support livetree.

Signed-off-by: Siva Durga Prasad Paladugu <siva.durga.paladugu@xilinx.com>
Signed-off-by: Vipul Kumar <vipul.kumar@xilinx.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>