vhost: fix packed ring index wrapping
vhost: fix packed ring index wrapping

Unlike split ring, packed ring does not mandate the ring size
to be a power of 2. So we have to use a modulo operation when
wrapping ring index.

Fixes: 873e8dad6f49 ("vhost: support packed ring in async datapath")
Cc: stable@dpdk.org

Signed-off-by: Maxime Coquelin <9a2667dee3b90866bbc9c2696cff2b7d5616c95a@redhat.com>
Acked-by: Cheng Jiang <7a6a77dd7576bfdf5dac8a9250f1050e5c53c3d0@intel.com>
Reviewed-by: Chenbo Xia <5d298a4585cd22ca5d29de25967a5599c4c324c8@intel.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk