PCI: dwc: Use DBI accessors

PCI: dwc: Use DBI accessors

Convert the remaining cases of register accesses using dbi_base rather
than dw_pcie_(read|write)[bwl]_dbi accessors.

Link: https://lore.kernel.org/r/20200821035420.380495-41-robh@kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Pratyush Anand <pratyush.anand@gmail.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Jonathan Hunter <jonathanh@nvidia.com>
Cc: linux-tegra@vger.kernel.org