tracing: Convert some timer events to DEFINE_EVENT

Use DECLARE_EVENT_CLASS, and save ~2.3K:

   text    data     bss     dec     hex filename
7018823 2031888 7251132 16301843         f8bf13 vmlinux.o.orig
7016727 2031696 7251132 16299555         f8b623 vmlinux.o

5 events are converted:

  timer_class:   timer_init, timer_expire_exit, timer_cancel
  hrtimer_class: hrtimer_init, hrtimer_cancel

No change in functionality.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4BFA3773.3060200@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>