s390/qdio: fix access to uninitialized qdio_q fields

Ever since CQ/QAOB support was added, calling qdio_free() straight after
qdio_alloc() results in qdio_release_memory() accessing uninitialized
memory (ie. q->u.out.use_cq and q->u.out.aobs). Followed by a
kmem_cache_free() on the random AOB addresses.

For older kernels that don't have 6e30c549, the same applies if
qdio_establish() fails in the DEV_STATE_ONLINE check.

While initializing q->u.out.use_cq would be enough to fix this
particular bug, the more future-proof change is to just zero-alloc the
whole struct.

Fixes: 104ea556

 ("qdio: support asynchronous delivery of storage blocks")
Cc: <stable@vger.kernel.org> #v3.2+
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>