ftrace/selftest: Have the reset_trigger code be a bit more careful

The trigger code is picky in how it can be disabled as there may be
dependencies between different events and synthetic events. Change the order
on how triggers are reset.

 1) Reset triggers of all synthetic events first
 2) Remove triggers with actions attached to them
 3) Remove all other triggers

If this order isn't followed, then some triggers will not be reset, and an
error may happen because a trigger is busy.

Cc: stable@vger.kernel.org
Fixes: cfa0963d ("kselftests/ftrace : Add event trigger testcases")
Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>