google/kukui: Enable RTC

Enable RTC so that we can see correct timestamp in CrOS eventlogs.

BUG=b:134461866
TEST='mosys eventlog list' shows correct timestamp on Kukui

Change-Id: Ie9ef7c9343c781e348429cd5376a4a5519641e16
Signed-off-by: You-Cheng Syu <youcheng@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/33356
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Hung-Te Lin <hungte@chromium.org>

src/mainboard/google/kukui/Kconfig

@@ -25,6 +25,7 @@ config VBOOT
 
 config BOARD_SPECIFIC_OPTIONS
 	def_bool y
+	select RTC
 	select SOC_MEDIATEK_MT8183
 	select BOARD_ROMSIZE_KB_8192
 	select MAINBOARD_HAS_CHROMEOS