arm64: zynqmp: Add support for Xilinx zcu100-revC

This board has 2GB of memory, i2c, sd, wifi sdio, spis, uarts, display
port and usbs.
Board is using fixed clocks because clock driver hasn't been merged yet.

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