perf script python: Move dsoname code to a new function

This patch creates a new function get_dsoname() and move the code which
gets the dsoname string to this function.

That's because in next patch, when we process LBR data, we will also
need get_dsoname() to return dsoname for branch from/to.
Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1527843663-32288-2-git-send-email-yao.jin@linux.intel.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/scripting-engines/trace-event-python.c

@@ -372,6 +372,19 @@ static PyObject *get_field_numeric_entry(struct event_format *event,
 	return obj;
 }
 
+static const char *get_dsoname(struct map *map)
+{
+	const char *dsoname = "[unknown]";
+
+	if (map && map->dso) {
+		if (symbol_conf.show_kernel_path && map->dso->long_name)
+			dsoname = map->dso->long_name;
+		else
+			dsoname = map->dso->name;
+	}
+
+	return dsoname;
+}
 
 static PyObject *python_process_callchain(struct perf_sample *sample,
 					 struct perf_evsel *evsel,
@@ -427,14 +440,8 @@ static PyObject *python_process_callchain(struct perf_sample *sample,
 		}
 
 		if (node->map) {
-			struct map *map = node->map;
-			const char *dsoname = "[unknown]";
-			if (map && map->dso) {
-				if (symbol_conf.show_kernel_path && map->dso->long_name)
-					dsoname = map->dso->long_name;
-				else
-					dsoname = map->dso->name;
-			}
+			const char *dsoname = get_dsoname(node->map);
+
 			pydict_set_item_string_decref(pyelem, "dso",
 					_PyUnicode_FromString(dsoname));
 		}