tracing: Kill destroy_preds() and destroy_file_preds()

destroy_preds() makes no sense.

The only caller, event_remove(), actually wants destroy_file_preds().
__trace_remove_event_call() does destroy_call_preds() which takes care
of call->filter.

And after the previous change we can simply remove destroy_preds() from
event_remove(), we are going to call remove_event_from_tracers() which
in turn calls remove_event_file_dir()->free_event_filter().

Link: http://lkml.kernel.org/p/20140715184813.GA20488@redhat.com



Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>