Merge branch 'pci/controller/dwc'

- Factor pcie_valid_speed() and pci_bus_speed2lnkctl2() out of bwctrl so
  they can be shared by the DWC core (Hans Zhang)

- Flush MSI writes from endpoint before unmapping the iATU, as we already
  do for MSI-X writes (Niklas Cassel)

- Unmap MSI iATU window before mapping MSI-X window, to avoid a subsequent
  MSI write using a disabled aperture and losing the interrupt (Niklas
  Cassel)

- Change endpoint .pre_init() and .init() callbacks to return errors and
  handle them (Marek Vasut)

* pci/controller/dwc:
  PCI: dwc: Handle return value from endpoint .pre_init callback
  PCI: dwc: Handle return value from endpoint .init callback
  PCI: dwc: ep: Fix unmap potentially unmapping the wrong iATU
  PCI: dwc: ep: Flush cached MSI write before unmapping the iATU
  PCI: dwc: Use common speed conversion function
  PCI: Move pci_bus_speed2lnkctl2() to public header
  PCI: Add public pcie_valid_speed() for shared validation