PCI: dwc: Allow overriding bridge pci_ops

PCI: dwc: Allow overriding bridge pci_ops

In preparation to allow drivers to set their own root and child pci_ops
instead of using the DWC specific config space ops, we need to make
the pci_host_bridge pointer available and move setting the bridge->ops
and bridge->child_ops pointer to before the .host_init() hook.

Link: https://lore.kernel.org/r/20200821035420.380495-4-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>