libpayload: Add SKU ID coreboot table support

This patch adds support to read the SKU ID entry from the coreboot table
that was recently added in coreboot.

Change-Id: I1c3b375da6119a4f8e8e7e25a11644becb90f927
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/22743
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

payloads/libpayload/include/coreboot_tables.h

@@ -239,6 +239,7 @@ struct cb_x86_rom_mtrr {
 
 #define CB_TAG_BOARD_ID		0x0025
 #define CB_TAG_RAM_CODE		0x0028
+#define CB_TAG_SKU_ID		0x002d
 struct cb_strapping_id {
 	uint32_t tag;
 	uint32_t size;