This change is specifically needed for the IXP2000 platform. IXP2000
platforms have various PCI devices with large memory space requirements
(~3.5 GB total sometimes) and a banked PCI window that allows for accessing
all 4GB of memory space.  The FW configures the devices on the bus in such
a way that standard linux drivers (e100, e1000, ide) can work w/o any changes
and places devices specific to Intel's closed source IXA sdk in regions of
PCI memory space that require using special registers on the IXP. This can
be accomplished in the kernel using a board-specific enumerator or a
lot of fixups, but it is far easier to just accept what the FW has provided.
Signed-off-by: Deepak Saxena <dsaxena@plexity.net>