edac: AMD8131 driver source file

Introduce AMD8131 EDAC driver source file, which makes use of error
detections on the PCI-X Bridge Controllers on the AMD8131 HyperTransport
PCI-X Tunnel.

Signed-off-by: Harry Ciao <qingtao.cao@windriver.com>
Cc: Doug Thompson <norsk5@yahoo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>