edac: add memory types strings for debugging

Instead of using deeply-nested conditionals for dumping the DIMM type in
debug mode, add a strings array of the supported DIMM types.

This is useful in cases where an edac driver supports multiple DRAM
types and is only defined in debug builds.

Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
diff --git a/drivers/edac/amd64_edac.c b/drivers/edac/amd64_edac.c
index c403af2e..708d065 100644
--- a/drivers/edac/amd64_edac.c
+++ b/drivers/edac/amd64_edac.c
@@ -1024,10 +1024,7 @@
 		type = (pvt->dclr0 & BIT(18)) ? MEM_DDR : MEM_RDDR;
 	}
 
-	debugf1("  Memory type is: %s\n",
-		(type == MEM_DDR2) ? "MEM_DDR2" :
-		(type == MEM_RDDR2) ? "MEM_RDDR2" :
-		(type == MEM_DDR) ? "MEM_DDR" : "MEM_RDDR");
+	debugf1("  Memory type is: %s\n", edac_mem_types[type]);
 
 	return type;
 }