PCI: designware: Move calculation of bus addresses to DRA7xx

Commit f4c55c5a ("PCI: designware: Program ATU with untranslated
address") added the calculation of PCI bus addresses in pcie-designware.c,
storing them in new fields added in struct pcie_port.  This calculation is
done for every DesignWare user even though it only applies to DRA7xx.

Move the calculation of the bus addresses to the DRA7xx driver to allow the
rework of DesignWare to use the new DT parsing API.

Signed-off-by: Gabriele Paoloni <gabriele.paoloni@huawei.com>
Signed-off-by: Zhou Wang <wangzhou1@hisilicon.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Pratyush Anand <pratyush.anand@gmail.com>