Some sm8250 platforms require additional clock to be enabled for PCIe to function. In case it is disabled, PCIe access will result in IOMMU timeouts. Add device tree binding and driver support for this clock. Changes since v2: - Split this clock handling from qcom_pcie_get_resources_2_7_0() - Change comment to point that the clock is required rather than optional Changes since v1: - Added Fixes: tags, as respective patches have hit the upstream Linux tree.