implement drm_pcie_get_speed_cap_mask()
implement drm_pcie_get_speed_cap_mask()

non integrated radeon >= r600 parts will now try to enable PCIe 2.0/3.0
speeds when the PCIe root port advertises the relevant speeds.

orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars