mb/google/rauru: Enable RTC

Enable RTC so that we can see the correct timestamp and date in
ChromeOS.

rauru-rev0 ~ # tail /var/log/eventtlog.txt
suspend_stress_test -c 5 --suspend_max=30 --suspend_min=30

rauru-rev0 ~ # date
Thu Nov  7 14:54:09 CST 2024

TEST=Build pass, check date in ChromeOS
BUG=b:355550460

Change-Id: I95822fc7646d41dbbc61258741a2a42988fc31d7
Signed-off-by: Jarried Lin <jarried.lin@mediatek.corp-partner.google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/85979
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Yidi Lin <yidilin@google.com>
Reviewed-by: Yu-Ping Wu <yupingso@google.com>

src/mainboard/google/rauru/Kconfig

@@ -37,6 +37,7 @@ config BOARD_SPECIFIC_OPTIONS
 	select COMMONLIB_STORAGE_MMC
 	select FW_CONFIG
 	select FW_CONFIG_SOURCE_CHROMEEC_CBI
+	select RTC
 
 config MAINBOARD_DIR
 	string

src/mainboard/google/rauru/romstage.c

@@ -11,6 +11,7 @@
 #include <soc/mt6363.h>
 #include <soc/mt6373.h>
 #include <soc/mt6685.h>
+#include <soc/mt6685_rtc.h>
 #include <soc/mtk_fsp.h>
 #include <soc/pcie.h>
 #include <soc/pll.h>
@@ -44,6 +45,8 @@ void platform_romstage_main(void)
 	dvfsrc_opp_level_mapping();
 	srclken_rc_init();
 	clk_buf_init();
+	if (CONFIG(RTC))
+		rtc_boot();
 	mtk_dram_init();
 	modem_power_down();
 	dvfs_init();