Add reference counting to the LED target so that multiple targets sharing the
same trigger don't cause any problems.

Signed-off-by: Adam Nielsen <a.nielsen@shikadi.net>

--

>> I've tested it and it works well for me, so subject to any feedback I believe
>> it is ready to be included.
> 
> You need to protect the list_add/list_del from concurrent operation.
> 
> You need to check the return value of
> 
> ledinternal->trigger_id = kzalloc(strlen(ledinfo->id) + 1, GFP_KERNEL);

Thanks for looking at it so quickly!  I've attached an updated patch which
hopefully addresses these issues.

Cheers,
Adam.