vhost-user: Change one_time to per_device request

vhost-user: Change one_time to per_device request

Some devices, like virtio-scsi, consist of one vhost_dev, while others, like
virtio-net, contain multiple vhost_devs. The QEMU vhost-user code has a
concept of one-time messages which is misleading. One-time messages are sent
once per operation on the device, not once for the lifetime of the device.
Therefore, as discussed in [1], vhost_user_one_time_request should be
renamed to vhost_user_per_device_request and the relevant comments updated
to match the real functionality.

[1] https://lore.kernel.org/qemu-devel/20230127083027-mutt-send-email-mst@kernel.org/

Signed-off-by: Tom Lonergan <tom.lonergan@nutanix.com>
Message-Id: <20230628163927.108171-2-tom.lonergan@nutanix.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com>