crypto/ipsec_mb: fix build with GCC 12

crypto/ipsec_mb: fix build with GCC 12

GCC 12 raises the following warning:

In function ‘__rte_ring_enqueue_elems_64’,
    inlined from ‘__rte_ring_enqueue_elems’ at
        ../lib/ring/rte_ring_elem_pvt.h:130:3,
    inlined from ‘__rte_ring_do_hts_enqueue_elem’ at
        ../lib/ring/rte_ring_hts_elem_pvt.h:196:3,
    inlined from ‘rte_ring_mp_hts_enqueue_burst_elem’ at
        ../lib/ring/rte_ring_hts.h:110:9,
    inlined from ‘rte_ring_enqueue_burst_elem’ at
        ../lib/ring/rte_ring_elem.h:577:10,
    inlined from ‘rte_ring_enqueue_burst’ at
        ../lib/ring/rte_ring.h:738:9,
    inlined from ‘process_op_bit’ at
        ../drivers/crypto/ipsec_mb/pmd_snow3g.c:425:16,
    inlined from ‘snow3g_pmd_dequeue_burst’ at
        ../drivers/crypto/ipsec_mb/pmd_snow3g.c:484:20:
../lib/ring/rte_ring_elem_pvt.h:68:44: error: array subscript 1 is
        outside array bounds of ‘struct rte_crypto_op[0]’
        [-Werror=array-bounds]
   68 |                         ring[idx + 1] = obj[i + 1];
      |                                         ~~~^~~~~~~
../drivers/crypto/ipsec_mb/pmd_snow3g.c: In function
        ‘snow3g_pmd_dequeue_burst’:
../drivers/crypto/ipsec_mb/pmd_snow3g.c:434:1: note:
        at offset 8 into object ‘op’ of size 8
  434 | snow3g_pmd_dequeue_burst(void *queue_pair,
      | ^~~~~~~~~~~~~~~~~~~~~~~~

Validate that one (exactly) op has been processed or return early.

Fixes: b537abdbee74 ("crypto/snow3g: support bit-level operations")
Cc: stable@dpdk.org
Signed-off-by: David Marchand <david.marchand@redhat.com>
Acked-by: Stephen Hemminger <stephen@networkplumber.org>