perf evsel: Adopt fprintf routine from 'perf evlist'

So that we can print all the details when debugging other tools,
when we have just evlists and evsels, not a perf.data file.

Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-mktq5fy2h5z7jyeqvvf5mbc8@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/evsel.h

@@ -243,4 +243,12 @@ static inline bool perf_evsel__is_group_leader(const struct perf_evsel *evsel)
 {
 	return evsel->leader == evsel;
 }
+
+struct perf_attr_details {
+	bool freq;
+	bool verbose;
+};
+
+int perf_evsel__fprintf(struct perf_evsel *evsel,
+			struct perf_attr_details *details, FILE *fp);
 #endif /* __PERF_EVSEL_H */