dt-bindings: xilinx: zynq: Add missing boards

The bindings were missing when the device-tree
files were added

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