Partial EC software sync implementation

Doesn't check the EC hash, but does jump to the correct image, for now
assuming the hash is good.

BUG=chrome-os-partner:11087
TEST=manual

- Power+refresh.  System boots.  EC is in RO (verify via 'ectool version')
- Create a BIOS signed *without* RO-normal.
- Power+refresh.  System boots.  EC ends up in A.
- ectool eventgetb.  Event 0x2000 IS present, indicating EC has rebooted
- ectool eventclearb -1
- Power button to shut down, then power button to power back on.
- ectool eventgetb.  Event 0x2000 is NOT present.
- crossystem recovery_request=123 && reboot.  System reboots to recovery mode
  and EC is in read-only (verify via EC console 'sysinfo')
- Power off and on.  System boots.  EC ends up in A again.

Change-Id: I39682d1bf7215c62a4b20613d029e78194b98826
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/27574
Reviewed-by: Bill Richardson <wfrichar@chromium.org>

firmware/include/vboot_struct.h

@@ -231,8 +231,10 @@ typedef struct VbKernelPreambleHeader {
 #define VBSD_BOOT_S3_RESUME             0x00000100
 /* Read-only firmware supports the normal/developer code path */
 #define VBSD_BOOT_RO_NORMAL_SUPPORT     0x00000200
-/* VbInit was told that the system has a virtual dev-switch */
+/* VbInit() was told that the system has a virtual dev-switch */
 #define VBSD_HONOR_VIRT_DEV_SWITCH      0x00000400
+/* VbInit() was told the system supports EC software sync */
+#define VBSD_EC_SOFTWARE_SYNC           0x00000800
 
 /* Result codes for VbSharedDataHeader.check_fw_a_result (and b_result) */
 #define VBSD_LF_CHECK_NOT_DONE          0