vhost: fix virtqueue not accessible

vhost: fix virtqueue not accessible

Log feature is disabled in vhost user, so that log address was invalid
when checking. Check whether log address is valid can work around it.
Log address should also be translated in packed ring virtqueue.

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