PCI: dwc: Remove dwc specific config accessor ops

Now that all the drivers needing custom config accessors have been
converted to define their own pci_ops, we can remove the DWC specific
function callbacks {rd,wr}_{own,other}_conf.

Link: https://lore.kernel.org/r/20200821035420.380495-13-robh@kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Jingoo Han <jingoohan1@gmail.com>
Cc: Gustavo Pimentel <gustavo.pimentel@synopsys.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>