target/iscsi: Convert timers to use timer_setup()

In preparation for unconditionally passing the struct timer_list pointer to
all timer callbacks, switch to using the new timer_setup() and from_timer()
to pass the timer pointer explicitly. Includes a fix for correcting an
on-stack timer usage.

Cc: "Nicholas A. Bellinger" <nab@linux-iscsi.org>
Cc: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Jiang Yi <jiangyilism@gmail.com>
Cc: Varun Prakash <varun@chelsio.com>
Cc: linux-scsi@vger.kernel.org
Cc: target-devel@vger.kernel.org
Reviewed-and-Tested-by: Bart Van Assche <Bart.VanAssche@wdc.com>
Signed-off-by: Kees Cook <keescook@chromium.org>