PCI: dwc: Ensure all outbound ATU windows are reset

The Layerscape driver clears the ATU registers which may have been
configured by the bootloader. Any driver could have the same issue
and doing it for all drivers doesn't hurt, so let's move it into the
common DWC code.

Link: https://lore.kernel.org/r/20201105211159.1814485-6-robh@kernel.org


Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Jingoo Han <jingoohan1@gmail.com>
Cc: Minghuan Lian <minghuan.Lian@nxp.com>
Cc: Mingkai Hu <mingkai.hu@nxp.com>
Cc: Roy Zang <roy.zang@nxp.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Jingoo Han <jingoohan1@gmail.com>
Cc: Gustavo Pimentel <gustavo.pimentel@synopsys.com>
Cc: linuxppc-dev@lists.ozlabs.org