target/tcmu: Use macro to call container_of in tcmu_cmd_time_out_show

This patch makes a tiny change that using TCMU_DEV in
tcmu_cmd_time_out_show so it is consistent with other functions.

Signed-off-by: Kenjiro Nakayama <nakayamakenjiro@gmail.com>
Reviewed-by: Mike Christie <mchristi@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>