mb/google/rex: add variant gpio tables for variant creation

BUG=b:276818954
TEST=new_variant_fulltest.sh rex0
BRANCH=None

Signed-off-by: YH Lin <yueherngl@google.com>
Change-Id: Iebc098f8d480ac3e1835b00861fd844d97f281a8
Reviewed-on: https://review.coreboot.org/c/coreboot/+/74257
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>
Reviewed-by: Subrata Banik <subratabanik@google.com>
Reviewed-by: Paul Fagerburg <pfagerburg@chromium.org>
Reviewed-by: Kapil Porwal <kapilporwal@google.com>

util/mainboard/google/rex0/template/Makefile.inc

@@ -0,0 +1,5 @@
+bootblock-y += gpio.c
+
+romstage-y += gpio.c
+
+ramstage-y += gpio.c

util/mainboard/google/rex0/template/gpio.c

@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include <baseboard/gpio.h>
+#include <baseboard/variants.h>
+#include <types.h>
+#include <soc/gpio.h>
+#include <vendorcode/google/chromeos/chromeos.h>
+
+const struct pad_config *variant_gpio_table(size_t *num)
+{
+	*num = 0;
+	return NULL;
+}
+
+const struct pad_config *variant_early_gpio_table(size_t *num)
+{
+	*num = 0;
+	return NULL;
+}
+
+static const struct cros_gpio cros_gpios[] = {
+};
+
+DECLARE_CROS_GPIOS(cros_gpios);
+
+const struct pad_config *variant_romstage_gpio_table(size_t *num)
+{
+	*num = 0;
+	return NULL;
+}