Now that all the platforms with custom config access handling define
their own pci_ops, let's split the default config accessors to use
different pci_ops for root and child buses. With this, we can use the
generic config accessors. The child bus accesses mainly require a
.map_bus() hook to reconfigure the iATU on each config space access.

Link: https://lore.kernel.org/r/20200821035420.380495-14-robh@kernel.orgSigned-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>