PCI: dwc: al: Use pci_ops for child config space accessors

Now that DWC drivers can setup their own pci_ops for the root and child
buses, convert the Amazon driver to use the standard pci_ops for child
bus config accesses.

Link: https://lore.kernel.org/r/20200821035420.380495-6-robh@kernel.org


Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Jonathan Chocron <jonnyc@amazon.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>