mb/google/octopus: Override VBT selection for Garg

Garg proto build has 3 SKUs:
 garg 2A2C DB: SKU ID - 1
 garg HDMI DB: SKU ID - 9
 garg LTE  DB: SKU ID - 17

For SKU#9, VBT will need to be overridden to enable DDI_C output to HDMI

BUG=b:134912735
BRANCH=octopus
TEST=emerge-octopus coreboot chromeos-bootimage
Cq-Depend: chrome-internal:1380847

Change-Id: I6c0ec086496eaf217ea8e326f5084d886d0e698f
Signed-off-by: Kevin Chiu <Kevin.Chiu@quantatw.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/33395
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Karthik Ramasubramanian <kramasub@google.com>

src/mainboard/google/octopus/variants/garg/Makefile.inc

@@ -1,3 +1,4 @@
 bootblock-y += gpio.c
 
 ramstage-y += gpio.c
+ramstage-y += variant.c

src/mainboard/google/octopus/variants/garg/variant.c

@@ -0,0 +1,39 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright 2019 Google LLC
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <boardid.h>
+#include <ec/google/chromeec/ec.h>
+#include <drivers/intel/gma/opregion.h>
+#include <baseboard/variants.h>
+
+enum {
+	SKU_1_2A2C = 1,
+	SKU_9_HDMI = 9,
+	SKU_17_LTE = 17,
+};
+
+const char *mainboard_vbt_filename(void)
+{
+	uint32_t sku_id;
+
+	sku_id = get_board_sku();
+
+	switch (sku_id) {
+	case SKU_9_HDMI:
+		return "vbt_garg_hdmi.bin";
+	default:
+		return "vbt.bin";
+	}
+}