pci: controller: dwc: qcom: Add PCIe support for SM8250 SoC

The PCIe IP on SM8250 SoC is similar to the one used on SDM845. Hence
the support is added reusing the 2.7.0 ops. Only difference is the need
of ATU base, which will be fetched opionally if provided by DT/ACPI.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>