arm64: zynqmp: Add support for Xilinx zc1751

Xilinx zc1751 boards is used for silicon validation. Board can be
extended with 5 FMCs/DCs cards to connect various IPs. Describe all
these combinations.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Rob Herring <robh@kernel.org>