ring-buffer: Remove ring_buffer_event_time_delta()

The ring_buffer_event_time_delta() static inline function does not
have any users. Remove it.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

include/linux/ring_buffer.h

@@ -62,18 +62,6 @@ enum ring_buffer_type {
 unsigned ring_buffer_event_length(struct ring_buffer_event *event);
 void *ring_buffer_event_data(struct ring_buffer_event *event);
 
-/**
- * ring_buffer_event_time_delta - return the delta timestamp of the event
- * @event: the event to get the delta timestamp of
- *
- * The delta timestamp is the 27 bit timestamp since the last event.
- */
-static inline unsigned
-ring_buffer_event_time_delta(struct ring_buffer_event *event)
-{
-	return event->time_delta;
-}
-
 /*
  * ring_buffer_discard_commit will remove an event that has not
  *   ben committed yet. If this is used, then ring_buffer_unlock_commit