Port of Linux commit 7bc082d

    Cleanup DBI read and write APIs by removing leading "__" (underscore)
    from their names as there is no reason to have leading underscores
    in the first place in the function definition.

    Remove dbi/dbi2 base address parameters as the same behaviour can be
    obtained through read and write APIs. Since dw_pcie_{readl/writel}_dbi()
    APIs can't be used for ATU read/write as ATU base address could be
    different from DBI base address, implement ATU read/write APIs using ATU
    base address without using dw_pcie_{readl/writel}_dbi() APIs.

    Signed-off-by: Vidya Sagar <vidyas@nvidia.com>
    Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
    Acked-by: Jingoo Han <jingoohan1@gmail.com>

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>