ir: bt_ctf_event_set_clock_value(): validate clock value's class

ir: bt_ctf_event_set_clock_value(): validate clock value's class

On bt_ctf_event_set_clock_value(): validate that the clock class of a
clock value is part of the event's trace object.

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>