vhost-scsi: Remove unnecessary forward struct vhost_scsi declaration

It was needed when struct tcm_vhost_tpg is in tcm_vhost.h
Signed-off-by: Asias He <asias@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vhost/scsi.c

@@ -116,7 +116,6 @@ struct tcm_vhost_nacl {
 	struct se_node_acl se_node_acl;
 };
 
-struct vhost_scsi;
 struct tcm_vhost_tpg {
 	/* Vhost port target portal group tag for TCM */
 	u16 tport_tpgt;