vhost: make IOTLB cache name unique among processes

vhost: make IOTLB cache name unique among processes

Currently, iotlb cache name is comprised of vid and virtqueue
index. For example, "iotlb_cache_0_0". Because vid is assigned
per process, iotlb cache name is not unique among multi processes.
For example a secondary process uses a vhost
(ex. eth_vhost0,iface=/tmp/sock0) and another secondary process
uses a vhost (ex. eth_vhost1,iface=/tmp/sock1), iotlb cache
name of both vhost ("iotlb_cache_0_0") are same and as a result
iotlb cache is broken.

This patch makes iotlb cache name unique among milti processes
by adding process id to the iotlb cache name.

The prefix of the name is shortened to "iotlb_" since the maximum
length of pool name is 25 bytes (RTE_MEMPOOL_NAMESIZE is 26).
Note that it is just 25 characters in maximum at the moment.
Here,
* pid_t == int: max 10 digits.
* vid < MAX_VHOST_DECICE(1024): max 4 digits.
* vq_index < VHOST_MAX_VRING(256): max 3 digits.

Fixes: d012d1f293f4 ("vhost: add IOTLB helper functions")
Cc: stable@dpdk.org
Signed-off-by: Itsuro Oda <oda@valinux.co.jp>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>