ipc/sem.c: always use only one queue for alter operations

There are two places that can contain alter operations:
 - the global queue: sma->pending_alter
 - the per-semaphore queues: sma->sem_base[].pending_alter.

Since one of the queues must be processed first, this causes an odd
priorization of the wakeups: complex operations have priority over
simple ops.

The patch restores the behavior of linux <=3.0.9: The longest waiting
operation has the highest priority.

This is done by using only one queue:
 - if there are complex ops, then sma->pending_alter is used.
 - otherwise, the per-semaphore queues are used.

As a side effect, do_smart_update_queue() becomes much simpler: no more
goto logic.

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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>