perf header: Prepare tracepoint events regardless of name

Current perf_evlist__set_tracepoint_names is a misnomer because it finds
and sets correspoding event_format in addition to the name.  So skipping
it when a event has set name already caused a trouble.

Rename it and set name only a event doesn't have one.

Reported-by: David Ahern <dsahern@gmail.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1346897446-16569-2-git-send-email-namhyung@kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>