target/tcm_fc: Rename ft_{add,del}_lport to {add,del}_wwn

These functions are not adding or deleting an lport. They are adding a
wwn that may match with an lport that is present on the system.

Renaming ft_del_lport also means we won't have functions named
both ft_del_lport and ft_lport_del any more.

Signed-off-by: Andy Grover <agrover@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>