armv8: cavium: Add the device tree for ThunderX

This commit adds the FDT for the ThunderX family of SoCs

Signed-off-by: Sergey Temerkhanov <s.temerkhanov@gmail.com>
Signed-off-by: Radha Mohan Chintakuntla <rchintakuntla@cavium.com>

Reviewed-by: Simon Glass <sjg@chromium.org>