lisa.trace: Add compat stub for Trace.df_events()
lisa.trace: Add compat stub for Trace.df_events()

Since df_events() has been renamed into df_event(), add a compatibility
stub under the old names.

credp/lisa,credp/lisa,ARM-software/lisa,ARM-software/lisa,credp/lisa,credp/lisa,ARM-software/lisa,ARM-software/lisa