tcm_fc: Simplify ft_send_work for tmr path

Check fc_tm_flags early and call ft_send_tm() right away. Don't need to
set local vars for tm case.

data_len local var now unneeded, remove.

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