ARM64: Add new Xilinx ZynqMP SoC

Initial version of device tree for Xilinx ZynqMP SoC.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Acked-by: Sören Brinkmann <soren.brinkmann@xilinx.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>