device/dram/ddr2.c: Store the checksum in the decoded SPD struct

Change-Id: I53f4a3e4030ea19e10c0fe11a99a3480644f5fae
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/21676
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Patrick Rudolph <siro@das-labor.org>

src/include/device/dram/ddr2.h

@@ -186,6 +186,7 @@ struct dimm_attr_st {
 	u32 tPLL;
 	u32 tRR;
 
+	u8 checksum;
 	/* Manufacturer ID */
 	u32 manufacturer_id;
 	/* ASCII part number - NULL terminated */