ipc/sem: separate wait-for-zero and alter tasks into seperate queues

ipc/sem: separate wait-for-zero and alter tasks into seperate queues

Introduce separate queues for operations that do not modify the semaphore
values.  Advantages:

- Simpler logic in check_restart().
- Faster update_queue(): Right now, all wait-for-zero operations
  are always tested, even if the semaphore value is not 0.
- wait-for-zero gets again priority, as in linux <=3.0.9

Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Davidlohr Bueso <davidlohr.bueso@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>