PCI: iproc: Add outbound mapping support

Certain SoCs require the PCIe outbound mapping to be configured in
software.  Add support for those chips.

[jonmason: Use %pap format when printing size_t to avoid warnings in 32-bit
build.]
[arnd: Use div64_u64() instead of "%" to avoid __aeabi_uldivmod link error
in 32-bit build.]
Signed-off-by: Ray Jui <rjui@broadcom.com>
Signed-off-by: Jon Mason <jonmason@broadcom.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>