target: Drop unused legacy target_core_fabric_ops API callers

This patch drops the following unused legacy API callers from target_core_fabric.h:

*) TFO->fall_back_to_erl0()
*) TFO->stop_session()
*) TFO->sess_logged_in()
*) TFO->is_state_remove()

This patch also removes the stub usage in loopback, tcm_fc, iscsi_target,
and ib_srpt fabric modules.

Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/tcm_fc/tfc_sess.c

@@ -338,20 +338,6 @@ void ft_sess_close(struct se_session *se_sess)
 	synchronize_rcu();		/* let transport deregister happen */
 }
 
-void ft_sess_stop(struct se_session *se_sess, int sess_sleep, int conn_sleep)
-{
-	struct ft_sess *sess = se_sess->fabric_sess_ptr;
-
-	pr_debug("port_id %x\n", sess->port_id);
-}
-
-int ft_sess_logged_in(struct se_session *se_sess)
-{
-	struct ft_sess *sess = se_sess->fabric_sess_ptr;
-
-	return sess->port_id != -1;
-}
-
 u32 ft_sess_get_index(struct se_session *se_sess)
 {
 	struct ft_sess *sess = se_sess->fabric_sess_ptr;
@@ -367,11 +353,6 @@ u32 ft_sess_get_port_name(struct se_session *se_sess,
 	return ft_format_wwn(buf, len, sess->port_name);
 }
 
-void ft_sess_set_erl0(struct se_session *se_sess)
-{
-	/* XXX TBD called when out of memory */
-}
-
 /*
  * libfc ops involving sessions.
  */