This adds /sys/power/wake_lock and /sys/power/wake_unlock. Writing a string to wake_lock creates a wake lock the first time is sees a string and locks it. Optionally, the string can be followed by a timeout. To unlock the wake lock, write the same string to wake_unlock. Change-Id: I66c6e3fe6487d17f9c2fafde1174042e57d15cd7