dt-bindings: firmware: xilinx: Add xlnx,zynqmp-firmware compatible

dt-bindings: firmware: xilinx: Add xlnx,zynqmp-firmware compatible

The absence of a compatible property caused dt_binding_check to skip
the zynqmp_firmware node.

To address this, add "xlnx,zynqmp-firmware" to the compatible property
in the example section for the zynqmp_firmware node.

Signed-off-by: Ronak Jain <ronak.jain@amd.com>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20251212100542.2756757-2-ronak.jain@amd.com
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>