vhost: protect log address translation in IOTLB update

vhost: protect log address translation in IOTLB update

Currently, the log address translation only  happens in the vhost-user's
translate_ring_addresses(). However, the IOTLB update handler is not
checking if it was mapped to re-trigger that translation.

Since the log address mapping could fail, check it on iotlb updates.
Also, check it on vring_translate() so we do not dirty pages if the
logging address is not yet ready.

Additionally, properly protect the accesses to the iotlb structures.

Fixes: fbda9f145927 ("vhost: translate incoming log address to GPA")
Cc: stable@dpdk.org
Signed-off-by: Adrian Moreno <amorenoz@redhat.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>