perf report: Create a symbol_conf flag for showing branch flag counting

Create a new flag show_branchflag_count in symbol_conf. The flag is used
to control if showing the branch flag counting information. The flag
depends on if the perf.data has branch data and if user chooses the
"branch-history" option in perf report command line.

Signed-off-by: Yao Jin <yao.jin@linux.intel.com>
Acked-by: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Linux-kernel@vger.kernel.org
Cc: Yao Jin <yao.jin@linux.intel.com>
Link: http://lkml.kernel.org/r/1477876794-30749-3-git-send-email-yao.jin@linux.intel.com


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