Name: RD9x0/RX980 Host Bridge
These 1002:5Axx entries are part of the northbridge, not the SBxxx southbridge.
I dug up some AMD documentation (http://support.amd.com/TechDocs/48692.pdf) and it appears the gfx0 port B is 5a17, and 5a14 is the 9xx series host bridge.
The one for the 890FX chipset (RD890) is under NDA but it appears from lspci entries that the RD890 uses basically the same id's except for its northbridge which is 5a11.
By the way GPP is not graphics port, it's for anything other than graphics.