perf hists: Make hist_entry__has_callchains() work with 'perf c2c'

Since 'perf c2c' uses 'struct hists' not allocated together with a
'struct perf_evsel' instance, we can't go from a 'struct hist_entry'
pointer to a 'struct perf_evsel' via he->hists, so, instead, check if
space was set aside for hist_entry->callchain[0] at hist_entry__new()
time.

Reported-by: Jin Yao <yao.jin@linux.intel.com>
Reported-by: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Fixes: fabd37b8 ("perf hists: Check if a hist_entry has callchains before using them")
Link: https://lkml.kernel.org/n/tip-e8ife8djvvvwmeze3s4yodii@git.kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>