SB800: Add IMC ROM and fan control.

Add configuration for AMD's IMC ROM and fan registers for cimx/sb800
platforms.

- Allows user to add the IMC rom to the build and to configure the
  location of the "signature" between the allowed positions.
- Allows for no fan control, manual setup of SB800 Fan registers, or
  setup of the IMC fan configuration registers.
- Register configuration is done through devicetree.cb. No files need
  to be added for new platform configuration.
- Initial setup is for Persimmon, but may be extended to any cimx/sb800
  platform.

Change-Id: Ib06408d794988cbb29eed6adbeeadea8b2629bae
Signed-off-by: Martin Roth <martin@se-eng.com>
Reviewed-on: http://review.coreboot.org/1977
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>
Reviewed-by: Marc Jones <marcj303@gmail.com>
diff --git a/src/southbridge/amd/cimx/sb800/SBPLATFORM.h b/src/southbridge/amd/cimx/sb800/SBPLATFORM.h
index 22d7724..1966eb4 100644
--- a/src/southbridge/amd/cimx/sb800/SBPLATFORM.h
+++ b/src/southbridge/amd/cimx/sb800/SBPLATFORM.h
@@ -57,6 +57,10 @@
 #endif
 #define FIXUP_PTR(ptr)  ptr
 
+#if CONFIG_SB800_IMC_FWM
+	#define IMC_ENABLE_OVER_WRITE        0x01
+#endif
+
 #include <console/console.h>
 #include "AmdSbLib.h"
 #include "Amd.h"