tcm_fc: Call lookup_tmr_lun() for all TM types

Don't see a reason to differentiate, so drop the fabric specific
switch statement in ft_send_tm() ahead of conversion to use
target_submit_tmr().

Signed-off-by: Andy Grover <agrover@redhat.com>
Cc: Kiran Patil <kiran.patil@intel.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>