perf evsel: Rename perf_evsel__is_*() to evsel__is*()

As those are 'struct evsel' methods, not part of tools/lib/perf/, aka
libperf, to whom the perf_ prefix belongs.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-diff.c

@@ -467,7 +467,7 @@ static struct evsel *evsel_match(struct evsel *evsel,
 	struct evsel *e;
 
 	evlist__for_each_entry(evlist, e) {
-		if (perf_evsel__match2(evsel, e))
+		if (evsel__match2(evsel, e))
 			return e;
 	}