blink driver power saving

The blink driver wakes up every jiffies which wastes power unnecessarily.
Using a notifier gives same effect. Also add ability to unload module.

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
[ We should really just delete the whole thing. The blink driver is
  broken in many other ways too  -Linus ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>