dt-bindings: pci: qcom: Document PCIe bindings for SM8450

Document the PCIe DT bindings for SM8450 SoC. The PCIe IP is similar
to the one used on SM8250, however unlike SM8250, PCIe0 and PCIe1 use
different set of clocks, so two compatible entries are required.

Link: https://lore.kernel.org/r/20220223101435.447839-2-dmitry.baryshkov@linaro.org


Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Acked-by: Stanimir Varbanov <svarbanov@mm-sol.com>