tracing: Have show_event_filters/triggers files take trace array ref

In the Linux kernel, the following vulnerability has been resolved:

tracing: Have show_event_filters/triggers files take trace array ref

The newly added files show_event_filters and show_event_triggers that show
all filters or triggers that are set within the trace array do not take a
reference for the trace array it is showing. Without taking a reference,
the trace_array may be freed via "rmdir" while a task is reading one of
theses files. Those files iterate all the events within an instance
(trace_array) and nothing prevents that instance from being freed while
its data is being read. This causes a use-after-free crash.

Have the open of both those files take the trace_array reference via the
trace_array_get() that prevents the trace_array from being freed while the
files are opened.