There are places where we have only access to struct hists and need to
know if any of its hist_entries has callchains, like when drawing
headers for the various output modes (stdio, TUI, etc), so, when adding
a new hist_entry, check if it has callchains, storing this info for
later use by hists__has_callchains().

This reimplementation is necessary because not always a 'struct hists'
is allocated together with a 'struct perf evsel', so we can't go from
'hists' to 'perf_event_attr.sample_type & PERF_SAMPLE_CALLCHAIN'.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jin Yao <yao.jin@linux.intel.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-hg5g7yddjio3ljwyqnnaj5dt@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>