mb/google/skywalker: Enable USB3_HUB_RST

We have to reset the USB hub as early as possible. Otherwise the USB3
hub may not be usable in the payload. This design has been introduced
since Cherry.

BUG=b:390357201
BRANCH=none
TEST=detect USB devices in depthcharge, and the log is like "Added USB
disk 2."

Change-Id: I4ee24aef2a887c8a30738912a8bf90f830a72bed
Signed-off-by: Cong Yang <yangcong5@huaqin.corp-partner.google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/87348
Reviewed-by: Yidi Lin <yidilin@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Yu-Ping Wu <yupingso@google.com>

src/mainboard/google/skywalker/bootblock.c

@@ -1,9 +1,18 @@
 /* SPDX-License-Identifier: GPL-2.0-only OR MIT */
 
 #include <bootblock_common.h>
+#include <gpio.h>
 #include <soc/spi.h>
 
+#include "gpio.h"
+
+static void usb3_hub_reset(void)
+{
+	gpio_output(GPIO_USB3_HUB_RST_L, 1);
+}
+
 void bootblock_mainboard_init(void)
 {
 	mtk_snfc_init();
+	usb3_hub_reset();
 }

src/mainboard/google/skywalker/gpio.h

@@ -6,5 +6,6 @@
 #include <soc/gpio.h>
 
 #define GPIO_XHCI_INIT_DONE	GPIO(GBE_MDC)
+#define GPIO_USB3_HUB_RST_L	GPIO(GPIO07)
 
 #endif