google/kukui: Enable CHROMEOS_USE_EC_WATCHDOG_FLAG

Kukui AP doesn't remember if the last AP reset was due to AP watchdog.
We need to enable CHROMEOS_USE_EC_WATCHDOG_FLAG so that it will query
the reset reason from EC.

BUG=b:109900671,b:118654976
BRANCH=none
TEST=1. run 'mosys eventlog clear; stop daisydog; echo > /dev/watchdog'
     2. wait for watchdog reset
     3. check 'mosys eventlog list | grep watchdog'

Change-Id: I053cc7664bbaf0d3fcae26ba9481a0ad700dca90
Signed-off-by: You-Cheng Syu <youcheng@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/31844
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Hung-Te Lin <hungte@chromium.org>

src/mainboard/google/kukui/Kconfig

@@ -29,6 +29,7 @@ config BOARD_SPECIFIC_OPTIONS
 	select SOC_MEDIATEK_MT8183
 	select BOARD_ROMSIZE_KB_8192
 	select MAINBOARD_HAS_CHROMEOS
+	select CHROMEOS_USE_EC_WATCHDOG_FLAG if CHROMEOS
 	select COMMON_CBFS_SPI_WRAPPER
 	select SPI_FLASH
 	select FATAL_ASSERTS