google/kukui: Notify EC that AP is in S0

We have a pin from AP to EC, called AP_IN_SLEEP_L (SRCLKENA0 on AP side,
pad R23) that is supposed to be high in S0, and low in S3 (and X/don't
care in S5).
This should be set as early as possible in bootblock.

BUG=b:113367227
TEST=make; boots and verified AP_IN_SLEEP_L GPIO is high.
BRANCH=None

Change-Id: Icd59fa366c162e7443b8932a851e65f110f551ab
Signed-off-by: Hung-Te Lin <hungte@chromium.org>
Reviewed-on: https://review.coreboot.org/28585
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Julius Werner <jwerner@google.com>

src/mainboard/google/kukui/bootblock.c

@@ -21,6 +21,7 @@
 #include "gpio.h"
 
 #define BOOTBLOCK_EN_L (GPIO(KPROW0))
+#define AP_IN_SLEEP_L (GPIO(SRCLKENA0))
 
 void bootblock_mainboard_init(void)
 {
@@ -29,6 +30,9 @@ void bootblock_mainboard_init(void)
 	/* Turn on real eMMC. */
 	gpio_output(BOOTBLOCK_EN_L, 1);
 
+	/* Declare we are in S0 */
+	gpio_output(AP_IN_SLEEP_L, 1);
+
 	mtk_spi_init(CONFIG_EC_GOOGLE_CHROMEEC_SPI_BUS, SPI_PAD0_MASK, 6 * MHz);
 	mtk_spi_init(CONFIG_BOOT_DEVICE_SPI_FLASH_BUS, SPI_PAD0_MASK, 26 * MHz);
 }