dt-bindings: PCI: qcom: Add sa8775p compatible

Add sa8775p platform to the binding.

Link: https://lore.kernel.org/linux-pci/1689960276-29266-2-git-send-email-quic_msarkar@quicinc.com
Signed-off-by: Mrinmay Sarkar <quic_msarkar@quicinc.com>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Manivannan Sadhasivam <mani@kernel.org>