perf report: Also do default setup for synthesized branch stacks

The 'perf report' tool will default to displaying branch stacks (-b
option) if they are present.  Make that also happen for synthesized
branch stacks.
Signed-off-by: NAdrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/1443186956-18718-11-git-send-email-adrian.hunter@intel.comSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-report.c

@@ -829,6 +829,9 @@ int cmd_report(int argc, const char **argv, const char *prefix __maybe_unused)
 	has_br_stack = perf_header__has_feat(&session->header,
 					     HEADER_BRANCH_STACK);
 
+	if (itrace_synth_opts.last_branch)
+		has_br_stack = true;
+
 	/*
 	 * Branch mode is a tristate:
 	 * -1 means default, so decide based on the file having branch data.