perf hists browser gtk: Use hist_entry__has_callchains()

Since we can't go from struct hists to struct evsel for all cases (c2c
is an exception) and we have access to the hist_entry, use
hist_entry__has_callchains() in the GTK+ hists browser to figure out
if callchains are available.

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-8owkgrruzzi5emvblwh4e6le@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>