PCI: designware: Use pci_scan_root_bus() for simplicity
PCI: designware: Use pci_scan_root_bus() for simplicity

After b97ea289cf6a ("PCI: Assign resources before drivers claim devices
(pci_scan_root_bus())"), pci_scan_root_bus() no longer adds the devices, so
it is equivalent to:

  pci_create_root_bus()
  pci_scan_child_bus()

Use pci_scan_root_bus() to simplify the code.

[bhelgaas: changelog]
Signed-off-by: Yijing Wang <ac442ed3e729ed4f09d087e9c319e1c47c72d6f1@huawei.com>
Signed-off-by: Bjorn Helgaas <f10ec01be0c6b54271af5c550cd257810bdf3268@google.com>
Reviewed-by: Lucas Stach <48c9e973d8f86eb0cdae200124c5925db7587c4e@pengutronix.de>
Acked-by: Jingoo Han <ef4fc1703356c7317681ccb0f7a24ace05d8f6b6@gmail.com>
CC: Mohit Kumar <e81db36ab52392345806c7bc8596be7c3b491eae@st.com>
KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs