mb/google/brya: Add GPIO stubs

Add stubbed out GPIO configuration and perform GPIO initialization
during bootblock and ramstage.

BUG=b:174266035
TEST=Build Test

Signed-off-by: Eric Lai <ericr_lai@compal.corp-partner.google.com>
Change-Id: Ia658ab4b466242cf8658abb239f19a9c0a03849a
Reviewed-on: https://review.coreboot.org/c/coreboot/+/48065
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
diff --git a/src/mainboard/google/brya/mainboard.c b/src/mainboard/google/brya/mainboard.c
index 3dc2c41..d7c3156 100644
--- a/src/mainboard/google/brya/mainboard.c
+++ b/src/mainboard/google/brya/mainboard.c
@@ -1,10 +1,14 @@
 /* SPDX-License-Identifier: GPL-2.0-or-later */
 
+#include <baseboard/variants.h>
 #include <device/device.h>
 
 static void mainboard_init(void *chip_info)
 {
-	/* TODO: Perform mainboard initialization */
+	const struct pad_config *pads;
+	size_t num;
+	pads = variant_gpio_table(&num);
+	gpio_configure_pads(pads, num);
 }
 
 static void mainboard_enable(struct device *dev)