baytrail: reboot with EC in S0 with no MRC cache and EC in RW

This improves boot time in 2 ways for a firmware upgrade:

1. Normally MRC would detect the S0 state without an MRC cache
   even though it's told to the S5 path. When it observes this
   state a cold reset occurs. The cold reset stays in S5 for
   at least 4 seconds which is time observed by the end user.

2. As the EC was running RW code before the reset after firmware
   upgrade it will still be running the older RW code. Vboot will
   then reboot the EC and the whole system to put the EC into RO
   mode so it can handle the RW update.

The issues are mitigated by detecting the system is in S0 with
no MRC cache and the EC isn't in RO mode. Therefore we can do the
reboot without waiting the 4 secs and the EC is running RO so
the 2nd reboot is not necessary.

BUG=chrome-os-partner:24133
BRANCH=rambi,squawks
TEST=Booted. Updated firmware while in OS. Rebooted. Noted the
     EC reboot before MRC execution.

Change-Id: I1c53d334a5e18c237a74ffbe96f263a7540cd8fe
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/182061
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: http://review.coreboot.org/5040
Tested-by: build bot (Jenkins)
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>

src/soc/intel/baytrail/romstage/raminit.c

@@ -32,6 +32,8 @@
 #include <baytrail/pci_devs.h>
 #include <baytrail/reset.h>
 #include <baytrail/romstage.h>
+#include <ec/google/chromeec/ec.h>
+#include <ec/google/chromeec/ec_commands.h>
 
 static void reset_system(void)
 {
@@ -131,6 +133,12 @@ void raminit(struct mrc_params *mp, int prev_sleep_state)
 		reset_system();
 	} else {
 		printk(BIOS_DEBUG, "No MRC cache found.\n");
+#if CONFIG_EC_GOOGLE_CHROMEEC
+		if (prev_sleep_state == 0) {
+			/* Ensure EC is running RO firmware. */
+			google_chromeec_check_ec_image(EC_IMAGE_RO);
+		}
+#endif
 	}
 
 	mrc_entry = cbfs_get_file_content(CBFS_DEFAULT_MEDIA, "mrc.bin", 0xab,