amd64_edac: Erratum #637 workaround

F15h CPUs may report a non-DRAM address when reporting an error address
belonging to a CC6 state save area. Add a workaround to detect this
condition and compute the actual DRAM address of the error as documented
in the Revision Guide for AMD Family 15h Models 00h-0Fh Processors.

Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>

drivers/edac/amd64_edac.h

@@ -196,6 +196,7 @@
 
 #define DCT_CFG_SEL			0x10C
 
+#define DRAM_LOCAL_NODE_BASE		0x120
 #define DRAM_LOCAL_NODE_LIM		0x124
 
 #define DRAM_BASE_HI			0x140