ARM: dts: qcom: sdx55: Add support for PCIe EP

Add support for PCIe Endpoint controller on the Qualcomm SDX55 platform.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20211126070520.28979-4-manivannan.sadhasivam@linaro.org