AGESA fam12 fam14 fam15: Use common agesa_readSpd()

Remove northbridge specific callouts for AGESA_READ_SPD.

Move low-level SMBus code to southbridge.

Change-Id: I5fc91c49d9ef8e0af1c4d8194f857c61ce417d1d
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/7113
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
diff --git a/src/southbridge/amd/cimx/sb800/Makefile.inc b/src/southbridge/amd/cimx/sb800/Makefile.inc
index 1c65eee..95daf70 100644
--- a/src/southbridge/amd/cimx/sb800/Makefile.inc
+++ b/src/southbridge/amd/cimx/sb800/Makefile.inc
@@ -22,7 +22,7 @@
 
 romstage-y += cfg.c
 romstage-y += early.c
-romstage-y += smbus.c
+romstage-y += smbus.c smbus_spd.c
 romstage-y += reset.c
 
 ramstage-y += cfg.c