tracing: Update create_system_filter() kernel-doc comment

commit f306cc82 ("tracing: Update event filters for multibuffer")
added the parameter @tr for create_system_filter().

commit bb9ef1cb ("tracing: Change apply_subsystem_event_filter()
paths to check file->system == dir") changed the parameter from @system to @dir.

Link: https://lkml.kernel.org/r/20210325161911.123452-1-hqjagain@gmail.comSigned-off-by: Qiujun Huang <hqjagain@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

kernel/trace/trace_events_filter.c

@@ -1693,6 +1693,7 @@ static void create_filter_finish(struct filter_parse_error *pe)
 
 /**
  * create_filter - create a filter for a trace_event_call
+ * @tr: the trace array associated with these events
  * @call: trace_event_call to create a filter for
  * @filter_str: filter string
  * @set_str: remember @filter_str and enable detailed error in filter
@@ -1741,8 +1742,8 @@ int create_event_filter(struct trace_array *tr,
 }
 
 /**
- * create_system_filter - create a filter for an event_subsystem
- * @system: event_subsystem to create a filter for
+ * create_system_filter - create a filter for an event subsystem
+ * @dir: the descriptor for the subsystem directory
  * @filter_str: filter string
  * @filterp: out param for created filter (always updated on return)
  *