arm64: zynqmp: Add Ethernet node for zcu1285 revA

This patch add ethernet node gem1 to zcu1285 RevB.
GMII to RGMII converter sits between MAC and external
phy connected over GMII to MAC and RGMMI to external phy

Signed-off-by: Harini Katakam <harini.katakam@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>