vhost: relax log address alignment

vhost: relax log address alignment

commit c2997fe35ca8abdf671315cbbccd34aa7bf249af ("vhost: relax used
address alignment") fixed the alignment for the used virtual address,
but not for the physical address used for logging.

That's a mistake: alignment should clearly be the same for virtual and
physical addresses,

Cc: stable@vger.kernel.org
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>