Fix up and document the AMD CS5530/CS5530A support

The previous code was pretty unreadable, undocumented and did some totally
unrelated things (such as mucking with the game port or port 0x92).

This version is tested with a 256 KB chip and should work for the
CS5530 and CS5530A.

Corresponding to flashrom svn r120 and coreboot v2 svn r2715.

Signed-off-by: Uwe Hermann <uwe@hermann-uwe.de>
Acked-by: Stefan Reinauer <stepan@coresystems.de>
diff --git a/README b/README
index 0c56cc1..627239a 100644
--- a/README
+++ b/README
@@ -150,7 +150,7 @@
 Supported Southbridges
 ----------------------
 
-AMD CS5530
+AMD CS5530/CS5530A
 AMD Geode SC1100
 AMD AMD-8111
 ATI SB400