PCI: dwc: keystone: Use pci_ops for config space accessors

PCI: dwc: keystone: Use pci_ops for config space accessors

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

Link: https://lore.kernel.org/r/20200821035420.380495-7-robh@kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Murali Karicheri <m-karicheri2@ti.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>