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: NRay Jui <rjui@broadcom.com>
Signed-off-by: NJon Mason <jonmason@broadcom.com>
Signed-off-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>