mb/google/skyrim: Configure GPIO 67 as an unused GPIO

GPIO 67 is not currently used on skyrim, so set it as no-connect.
Since it's now free for other purposes, make sure that the
SPI-ROM-SHARING functionality is disabled.

BUG=b:268330591
TEST=Examine registers after change

Signed-off-by: Martin Roth <gaumless@gmail.com>
Change-Id: Id083baf41d25920eca09795453a01aac1d00d0f5
Reviewed-on: https://review.coreboot.org/c/coreboot/+/72908
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Jon Murphy <jpmurphy@google.com>
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>

src/mainboard/google/skyrim/Kconfig

@@ -15,6 +15,7 @@ config BOARD_SPECIFIC_OPTIONS
 	def_bool y
 	select AMD_SOC_CONSOLE_UART
 	select BOARD_ROMSIZE_KB_16384
+	select DISABLE_SPI_FLASH_ROM_SHARING
 	select DRIVERS_GENERIC_GPIO_KEYS
 	select DRIVERS_GENERIC_MAX98357A
 	select DRIVERS_ACPI_THERMAL_ZONE

src/mainboard/google/skyrim/variants/baseboard/gpio.c

@@ -73,8 +73,8 @@ static const struct soc_amd_gpio base_gpio_table[] = {
 	/* WWAN_RST_L */
 	PAD_GPO(GPIO_42, HIGH),
 	/* GPIO_43 - GPIO_66: Not available */
-	/* GPIO_67 */
-	PAD_GPI(GPIO_67, PULL_NONE),
+	/* GPIO_67 (Unused) */
+	PAD_NC(GPIO_67),
 	/* ESPI1_DATA2 */
 	PAD_NF(GPIO_68, SPI1_DAT2, PULL_NONE),
 	/* ESPI1_DATA3 */