dt-bindings: PCI: qcom,pcie-sc8280xp: Move SC8280XP to dedicated schema

Move SC8280XP compatible PCIe devices from qcom,pcie.yaml binding to a
dedicated file to make reviewing easier.

This creates equivalent schema file, except missing required compatible
which is actually redundant.

Link: https://lore.kernel.org/linux-pci/20240126-dt-bindings-pci-qcom-split-v3-6-f23cda4d74c0@linaro.org


Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>