dt-bindings: PCI: xilinx-xdma: Add schemas for Xilinx XDMA PCIe Root Port Bridge

Add YAML devicetree schemas for Xilinx XDMA Soft IP PCIe Root Port Bridge.

[kwilczynski: commit log]
Link: https://lore.kernel.org/linux-pci/20231003173453.938190-3-thippeswamy.havalige@amd.com
Signed-off-by: Thippeswamy Havalige <thippeswamy.havalige@amd.com>
Signed-off-by: Bharat Kumar Gogada <bharat.kumar.gogada@amd.com>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>