tools lib traceevent: Rename tep_free_format() to tep_free_event()

tools lib traceevent: Rename tep_free_format() to tep_free_event()

In order to make libtraceevent into a proper library, variables, data
structures and functions require a unique prefix to prevent name space
conflicts. This renames tep_free_format() to tep_free_event(), which
describes more closely the purpose of the function.

Signed-off-by: Tzvetomir Stoyanov <tstoyanov@vmware.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/20181130154647.591673556@goodmis.org
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>