tcm_fc: Convert call_rcu() to kfree_rcu(), drop ft_tport_rcu_free()

The call_rcu() in ft_tport_delete() invokes ft_tport_rcu_free(),
which just does a kfree().  So convert the call_rcu() to kfree_rcu(),
allowing ft_tport_rcu_free() to be eliminated.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: "Nicholas A. Bellinger" <nab@linux-iscsi.org>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Jesper Juhl <jj@chaosbits.net>
Cc: linux-scsi@vger.kernel.org
Cc: target-devel@vger.kernel.org