This dumps the EC panic information from the previous reboot.

Similar to the information presented by ectool panicinfo, except
that we do not bother doing any parsing (we should write a small
offline tool for that).
Signed-off-by: Nicolas Boichat <drinkcat@chromium.org>
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Tested-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Signed-off-by: Benson Leung <bleung@chromium.org>