Its common to have the (evsel->attr.sample_type & PERF_SAMPLE_CALLCHAIN),
so add an evsel__has_callchain(evsel) helper.

This will actually get more uses as we check that instead of
symbol_conf.use_callchain in places where that produces the same result
but makes this decision to be more fine grained, per evsel.

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-145340oytbthatpfeaq1do18@git.kernel.orgSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>