perf hists: Introduce hist_entry__has_callchain() method

We'll use this helper more frequently when reworking
symbol_conf.use_callchain logic, where knowing if a hist_entry has
callchains is the important bit, so make going from hist_entry to hists
to evsel easier, compact.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-p6gioxkzpkpz71dtt4wcs36o@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/sort.h

@@ -151,6 +151,12 @@ struct hist_entry {
 	struct callchain_root	callchain[0]; /* must be last member */
 };
 
+static __pure inline bool hist_entry__has_callchains(struct hist_entry *he)
+{
+	const struct perf_evsel *evsel = hists_to_evsel(he->hists);
+	return evsel__has_callchain(evsel);
+}
+
 static inline bool hist_entry__has_pairs(struct hist_entry *he)
 {
 	return !list_empty(&he->pairs.node);