cr50_enable_update: Add printk before EC hibernate

Add printout before EC hibernates during a cr50 update to clarify that
failure is due to EC rather than cr50.  Ran into a situation where DUT
shut down during cr50 update and the EC was the culprit.

BUG=None
BRANCH=None
TEST=None

Change-Id: I54813fec123de69604d1da4dfc65eaeb77d1662e
Signed-off-by: Shelley Chen <shchen@chromium.org>
Reviewed-on: https://review.coreboot.org/22120
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>

src/vendorcode/google/chromeos/cr50_enable_update.c

@@ -61,6 +61,7 @@ static void enable_update(void *unused)
 
 	if (IS_ENABLED(CONFIG_POWER_OFF_ON_CR50_UPDATE)) {
 		if (IS_ENABLED(CONFIG_EC_GOOGLE_CHROMEEC))
+			printk(BIOS_INFO, "Hibernating EC.\n");
 			google_chromeec_reboot(0, EC_REBOOT_HIBERNATE,
 				EC_REBOOT_FLAG_ON_AP_SHUTDOWN);
 		poweroff();