perf evsel: Propagate error info from tp_format

Propagate error info from tp_format via ERR_PTR to get it all the way
down to the parse-event.c tracepoint adding routines. Following
functions now return pointer with encoded error:

  - tp_format
  - trace_event__tp_format
  - perf_evsel__newtp_idx
  - perf_evsel__newtp

This affects several other places in perf, that cannot use pointer check
anymore, but must utilize the err.h interface, when getting error
information from above functions list.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Raphael Beamonte <raphael.beamonte@gmail.com>
Link: http://lkml.kernel.org/r/1441615087-13886-5-git-send-email-jolsa@kernel.org
[ Add two missing ERR_PTR() and one IS_ERR() ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
index f164a14..62ab307 100644
--- a/tools/perf/util/evsel.h
+++ b/tools/perf/util/evsel.h
@@ -160,6 +160,9 @@
 
 struct perf_evsel *perf_evsel__newtp_idx(const char *sys, const char *name, int idx);
 
+/*
+ * Returns pointer with encoded error via <linux/err.h> interface.
+ */
 static inline struct perf_evsel *perf_evsel__newtp(const char *sys, const char *name)
 {
 	return perf_evsel__newtp_idx(sys, name, 0);