alf_queue: ACCESS_ONCE() is needed for shared store marking deq done

There were missing a ACCESS_ONCE() when storing to the shared
variable q->consumer.tail.  This is mostly done to restrict the
compiler from doing too smart optimizations.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
alf_queue: minor optimization of moving mask outside loop

Moving reading q->mask out to seperate local variable "mask".
This optimization is likely already done by the compiler, but
lets just point it out explicitly for the compiler ;-)

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>