arm64: zynqmp: Add ethernet node for zcu1275 revB

This patch add ethernet node gem1 to zcu1275 RevB.
GMII to RGMII converter sits between MAC and external
phy connected over GMII to MAC and RGMMI to external phy.

Signed-off-by: Siva Durga Prasad Paladugu <siva.durga.paladugu@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>