vhost-scsi: Drop device mutex use in vhost_scsi_do_plug

We don't need the device mutex in vhost_scsi_do_plug because:
1. we have the vhost_scsi_mutex so the tpg->vhost_scsi pointer will not
change on us and the vhost_scsi can't be freed from under us if it was
set.
2. vhost_scsi_clear_endpoint will stop the virtqueues and flush them while
holding the vhost_scsi_mutex so we know once vhost_scsi_clear_endpoint
has completed that vhost_scsi_do_plug can't send new events and any
queued ones have completed.

So this patch drops the device mutex use in vhost_scsi_do_plug.
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Message-Id: <20230321020624.13323-5-michael.christie@oracle.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vhost/scsi.c

@@ -2003,8 +2003,6 @@ vhost_scsi_do_plug(struct vhost_scsi_tpg *tpg,
 	if (!vs)
 		return;
 
-	mutex_lock(&vs->dev.mutex);
-
 	if (plug)
 		reason = VIRTIO_SCSI_EVT_RESET_RESCAN;
 	else
@@ -2016,7 +2014,6 @@ vhost_scsi_do_plug(struct vhost_scsi_tpg *tpg,
 		vhost_scsi_send_evt(vs, tpg, lun,
 				   VIRTIO_SCSI_T_TRANSPORT_RESET, reason);
 	mutex_unlock(&vq->mutex);
-	mutex_unlock(&vs->dev.mutex);
 }
 
 static void vhost_scsi_hotplug(struct vhost_scsi_tpg *tpg, struct se_lun *lun)